diff --git a/admin.go b/admin.go
index a2aa7e5cb..db44aa380 100644
--- a/admin.go
+++ b/admin.go
@@ -12,9 +12,9 @@ type adminResponse struct {
 	Error string `json:"error"`
 }
 
-func adminRequest(ctx context.Context, client HTTPRequester, method string, teamName string, values url.Values, debug bool) (*adminResponse, error) {
+func adminRequest(ctx context.Context, client httpClient, method string, teamName string, values url.Values, d debug) (*adminResponse, error) {
 	adminResponse := &adminResponse{}
-	err := parseAdminResponse(ctx, client, method, teamName, values, adminResponse, debug)
+	err := parseAdminResponse(ctx, client, method, teamName, values, adminResponse, d)
 	if err != nil {
 		return nil, err
 	}
@@ -40,7 +40,7 @@ func (api *Client) DisableUserContext(ctx context.Context, teamName string, uid
 		"_attempts":  {"1"},
 	}
 
-	_, err := adminRequest(ctx, api.httpclient, "setInactive", teamName, values, api.debug)
+	_, err := adminRequest(ctx, api.httpclient, "setInactive", teamName, values, api)
 	if err != nil {
 		return fmt.Errorf("Failed to disable user with id '%s': %s", uid, err)
 	}
@@ -67,7 +67,7 @@ func (api *Client) InviteGuestContext(ctx context.Context, teamName, channel, fi
 		"_attempts":        {"1"},
 	}
 
-	_, err := adminRequest(ctx, api.httpclient, "invite", teamName, values, api.debug)
+	_, err := adminRequest(ctx, api.httpclient, "invite", teamName, values, api)
 	if err != nil {
 		return fmt.Errorf("Failed to invite single-channel guest: %s", err)
 	}
@@ -94,7 +94,7 @@ func (api *Client) InviteRestrictedContext(ctx context.Context, teamName, channe
 		"_attempts":  {"1"},
 	}
 
-	_, err := adminRequest(ctx, api.httpclient, "invite", teamName, values, api.debug)
+	_, err := adminRequest(ctx, api.httpclient, "invite", teamName, values, api)
 	if err != nil {
 		return fmt.Errorf("Failed to restricted account: %s", err)
 	}
@@ -118,7 +118,7 @@ func (api *Client) InviteToTeamContext(ctx context.Context, teamName, firstName,
 		"_attempts":  {"1"},
 	}
 
-	_, err := adminRequest(ctx, api.httpclient, "invite", teamName, values, api.debug)
+	_, err := adminRequest(ctx, api.httpclient, "invite", teamName, values, api)
 	if err != nil {
 		return fmt.Errorf("Failed to invite to team: %s", err)
 	}
@@ -140,7 +140,7 @@ func (api *Client) SetRegularContext(ctx context.Context, teamName, user string)
 		"_attempts":  {"1"},
 	}
 
-	_, err := adminRequest(ctx, api.httpclient, "setRegular", teamName, values, api.debug)
+	_, err := adminRequest(ctx, api.httpclient, "setRegular", teamName, values, api)
 	if err != nil {
 		return fmt.Errorf("Failed to change the user (%s) to a regular user: %s", user, err)
 	}
@@ -162,7 +162,7 @@ func (api *Client) SendSSOBindingEmailContext(ctx context.Context, teamName, use
 		"_attempts":  {"1"},
 	}
 
-	_, err := adminRequest(ctx, api.httpclient, "sendSSOBind", teamName, values, api.debug)
+	_, err := adminRequest(ctx, api.httpclient, "sendSSOBind", teamName, values, api)
 	if err != nil {
 		return fmt.Errorf("Failed to send SSO binding email for user (%s): %s", user, err)
 	}
@@ -185,7 +185,7 @@ func (api *Client) SetUltraRestrictedContext(ctx context.Context, teamName, uid,
 		"_attempts":  {"1"},
 	}
 
-	_, err := adminRequest(ctx, api.httpclient, "setUltraRestricted", teamName, values, api.debug)
+	_, err := adminRequest(ctx, api.httpclient, "setUltraRestricted", teamName, values, api)
 	if err != nil {
 		return fmt.Errorf("Failed to ultra-restrict account: %s", err)
 	}
@@ -207,7 +207,7 @@ func (api *Client) SetRestrictedContext(ctx context.Context, teamName, uid strin
 		"_attempts":  {"1"},
 	}
 
-	_, err := adminRequest(ctx, api.httpclient, "setRestricted", teamName, values, api.debug)
+	_, err := adminRequest(ctx, api.httpclient, "setRestricted", teamName, values, api)
 	if err != nil {
 		return fmt.Errorf("Failed to restrict account: %s", err)
 	}
diff --git a/bots.go b/bots.go
index 92570a049..e27e76ab6 100644
--- a/bots.go
+++ b/bots.go
@@ -19,9 +19,9 @@ type botResponseFull struct {
 	SlackResponse
 }
 
-func botRequest(ctx context.Context, client HTTPRequester, path string, values url.Values, debug bool) (*botResponseFull, error) {
+func botRequest(ctx context.Context, client httpClient, path string, values url.Values, d debug) (*botResponseFull, error) {
 	response := &botResponseFull{}
-	err := postSlackMethod(ctx, client, path, values, response, debug)
+	err := postSlackMethod(ctx, client, path, values, response, d)
 	if err != nil {
 		return nil, err
 	}
@@ -43,7 +43,7 @@ func (api *Client) GetBotInfoContext(ctx context.Context, bot string) (*Bot, err
 		"bot":   {bot},
 	}
 
-	response, err := botRequest(ctx, api.httpclient, "bots.info", values, api.debug)
+	response, err := botRequest(ctx, api.httpclient, "bots.info", values, api)
 	if err != nil {
 		return nil, err
 	}
diff --git a/bots_test.go b/bots_test.go
index 7066e78fc..3eab4e274 100644
--- a/bots_test.go
+++ b/bots_test.go
@@ -24,7 +24,7 @@ func TestGetBotInfo(t *testing.T) {
 	http.HandleFunc("/bots.info", getBotInfo)
 
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 
 	bot, err := api.GetBotInfo("B02875YLA")
diff --git a/channels.go b/channels.go
index 6204315a9..007985bc1 100644
--- a/channels.go
+++ b/channels.go
@@ -26,9 +26,9 @@ type Channel struct {
 	Locale    string `json:"locale"`
 }
 
-func channelRequest(ctx context.Context, client HTTPRequester, path string, values url.Values, debug bool) (*channelResponseFull, error) {
+func channelRequest(ctx context.Context, client httpClient, path string, values url.Values, d debug) (*channelResponseFull, error) {
 	response := &channelResponseFull{}
-	err := postForm(ctx, client, SLACK_API+path, values, response, debug)
+	err := postForm(ctx, client, APIURL+path, values, response, d)
 	if err != nil {
 		return nil, err
 	}
@@ -52,7 +52,7 @@ func (api *Client) ArchiveChannelContext(ctx context.Context, channelID string)
 		"channel": {channelID},
 	}
 
-	_, err = channelRequest(ctx, api.httpclient, "channels.archive", values, api.debug)
+	_, err = channelRequest(ctx, api.httpclient, "channels.archive", values, api)
 	return err
 }
 
@@ -70,7 +70,7 @@ func (api *Client) UnarchiveChannelContext(ctx context.Context, channelID string
 		"channel": {channelID},
 	}
 
-	_, err = channelRequest(ctx, api.httpclient, "channels.unarchive", values, api.debug)
+	_, err = channelRequest(ctx, api.httpclient, "channels.unarchive", values, api)
 	return err
 }
 
@@ -88,7 +88,7 @@ func (api *Client) CreateChannelContext(ctx context.Context, channelName string)
 		"name":  {channelName},
 	}
 
-	response, err := channelRequest(ctx, api.httpclient, "channels.create", values, api.debug)
+	response, err := channelRequest(ctx, api.httpclient, "channels.create", values, api)
 	if err != nil {
 		return nil, err
 	}
@@ -133,7 +133,7 @@ func (api *Client) GetChannelHistoryContext(ctx context.Context, channelID strin
 		}
 	}
 
-	response, err := channelRequest(ctx, api.httpclient, "channels.history", values, api.debug)
+	response, err := channelRequest(ctx, api.httpclient, "channels.history", values, api)
 	if err != nil {
 		return nil, err
 	}
@@ -154,7 +154,7 @@ func (api *Client) GetChannelInfoContext(ctx context.Context, channelID string)
 		"channel": {channelID},
 	}
 
-	response, err := channelRequest(ctx, api.httpclient, "channels.info", values, api.debug)
+	response, err := channelRequest(ctx, api.httpclient, "channels.info", values, api)
 	if err != nil {
 		return nil, err
 	}
@@ -167,7 +167,7 @@ func (api *Client) InviteUserToChannel(channelID, user string) (*Channel, error)
 	return api.InviteUserToChannelContext(context.Background(), channelID, user)
 }
 
-// InviteUserToChannelCustom invites a user to a given channel and returns a *Channel with a custom context
+// InviteUserToChannelContext invites a user to a given channel and returns a *Channel with a custom context
 // see https://api.slack.com/methods/channels.invite
 func (api *Client) InviteUserToChannelContext(ctx context.Context, channelID, user string) (*Channel, error) {
 	values := url.Values{
@@ -176,7 +176,7 @@ func (api *Client) InviteUserToChannelContext(ctx context.Context, channelID, us
 		"user":    {user},
 	}
 
-	response, err := channelRequest(ctx, api.httpclient, "channels.invite", values, api.debug)
+	response, err := channelRequest(ctx, api.httpclient, "channels.invite", values, api)
 	if err != nil {
 		return nil, err
 	}
@@ -197,7 +197,7 @@ func (api *Client) JoinChannelContext(ctx context.Context, channelName string) (
 		"name":  {channelName},
 	}
 
-	response, err := channelRequest(ctx, api.httpclient, "channels.join", values, api.debug)
+	response, err := channelRequest(ctx, api.httpclient, "channels.join", values, api)
 	if err != nil {
 		return nil, err
 	}
@@ -218,7 +218,7 @@ func (api *Client) LeaveChannelContext(ctx context.Context, channelID string) (b
 		"channel": {channelID},
 	}
 
-	response, err := channelRequest(ctx, api.httpclient, "channels.leave", values, api.debug)
+	response, err := channelRequest(ctx, api.httpclient, "channels.leave", values, api)
 	if err != nil {
 		return false, err
 	}
@@ -241,7 +241,7 @@ func (api *Client) KickUserFromChannelContext(ctx context.Context, channelID, us
 		"user":    {user},
 	}
 
-	_, err = channelRequest(ctx, api.httpclient, "channels.kick", values, api.debug)
+	_, err = channelRequest(ctx, api.httpclient, "channels.kick", values, api)
 	return err
 }
 
@@ -261,7 +261,7 @@ func (api *Client) GetChannelsContext(ctx context.Context, excludeArchived bool)
 		values.Add("exclude_archived", "1")
 	}
 
-	response, err := channelRequest(ctx, api.httpclient, "channels.list", values, api.debug)
+	response, err := channelRequest(ctx, api.httpclient, "channels.list", values, api)
 	if err != nil {
 		return nil, err
 	}
@@ -288,7 +288,7 @@ func (api *Client) SetChannelReadMarkContext(ctx context.Context, channelID, ts
 		"ts":      {ts},
 	}
 
-	_, err = channelRequest(ctx, api.httpclient, "channels.mark", values, api.debug)
+	_, err = channelRequest(ctx, api.httpclient, "channels.mark", values, api)
 	return err
 }
 
@@ -309,7 +309,7 @@ func (api *Client) RenameChannelContext(ctx context.Context, channelID, name str
 
 	// XXX: the created entry in this call returns a string instead of a number
 	// so I may have to do some workaround to solve it.
-	response, err := channelRequest(ctx, api.httpclient, "channels.rename", values, api.debug)
+	response, err := channelRequest(ctx, api.httpclient, "channels.rename", values, api)
 	if err != nil {
 		return nil, err
 	}
@@ -331,7 +331,7 @@ func (api *Client) SetChannelPurposeContext(ctx context.Context, channelID, purp
 		"purpose": {purpose},
 	}
 
-	response, err := channelRequest(ctx, api.httpclient, "channels.setPurpose", values, api.debug)
+	response, err := channelRequest(ctx, api.httpclient, "channels.setPurpose", values, api)
 	if err != nil {
 		return "", err
 	}
@@ -353,7 +353,7 @@ func (api *Client) SetChannelTopicContext(ctx context.Context, channelID, topic
 		"topic":   {topic},
 	}
 
-	response, err := channelRequest(ctx, api.httpclient, "channels.setTopic", values, api.debug)
+	response, err := channelRequest(ctx, api.httpclient, "channels.setTopic", values, api)
 	if err != nil {
 		return "", err
 	}
@@ -374,7 +374,7 @@ func (api *Client) GetChannelRepliesContext(ctx context.Context, channelID, thre
 		"channel":   {channelID},
 		"thread_ts": {thread_ts},
 	}
-	response, err := channelRequest(ctx, api.httpclient, "channels.replies", values, api.debug)
+	response, err := channelRequest(ctx, api.httpclient, "channels.replies", values, api)
 	if err != nil {
 		return nil, err
 	}
diff --git a/chat.go b/chat.go
index 8cc6bdefd..ece17292f 100644
--- a/chat.go
+++ b/chat.go
@@ -96,26 +96,24 @@ func (api *Client) DeleteMessageContext(ctx context.Context, channel, messageTim
 // PostMessage sends a message to a channel.
 // Message is escaped by default according to https://api.slack.com/docs/formatting
 // Use http://davestevens.github.io/slack-message-builder/ to help crafting your message.
-func (api *Client) PostMessage(channel, text string, params PostMessageParameters) (string, string, error) {
+func (api *Client) PostMessage(channelID string, options ...MsgOption) (string, string, error) {
 	respChannel, respTimestamp, _, err := api.SendMessageContext(
 		context.Background(),
-		channel,
-		MsgOptionText(text, params.EscapeText),
-		MsgOptionAttachments(params.Attachments...),
-		MsgOptionPostMessageParameters(params),
+		channelID,
+		MsgOptionPost(),
+		MsgOptionCompose(options...),
 	)
 	return respChannel, respTimestamp, err
 }
 
 // PostMessageContext sends a message to a channel with a custom context
-// For more details, see PostMessage documentation
-func (api *Client) PostMessageContext(ctx context.Context, channel, text string, params PostMessageParameters) (string, string, error) {
+// For more details, see PostMessage documentation.
+func (api *Client) PostMessageContext(ctx context.Context, channelID string, options ...MsgOption) (string, string, error) {
 	respChannel, respTimestamp, _, err := api.SendMessageContext(
 		ctx,
-		channel,
-		MsgOptionText(text, params.EscapeText),
-		MsgOptionAttachments(params.Attachments...),
-		MsgOptionPostMessageParameters(params),
+		channelID,
+		MsgOptionPost(),
+		MsgOptionCompose(options...),
 	)
 	return respChannel, respTimestamp, err
 }
@@ -135,18 +133,18 @@ func (api *Client) PostEphemeral(channelID, userID string, options ...MsgOption)
 // PostEphemeralContext sends an ephemeal message to a user in a channel with a custom context
 // For more details, see PostEphemeral documentation
 func (api *Client) PostEphemeralContext(ctx context.Context, channelID, userID string, options ...MsgOption) (timestamp string, err error) {
-	_, timestamp, _, err = api.SendMessageContext(ctx, channelID, append(options, MsgOptionPostEphemeral2(userID))...)
+	_, timestamp, _, err = api.SendMessageContext(ctx, channelID, MsgOptionPostEphemeral(userID), MsgOptionCompose(options...))
 	return timestamp, err
 }
 
 // UpdateMessage updates a message in a channel
-func (api *Client) UpdateMessage(channelID, timestamp, text string) (string, string, string, error) {
-	return api.UpdateMessageContext(context.Background(), channelID, timestamp, text)
+func (api *Client) UpdateMessage(channelID, timestamp string, options ...MsgOption) (string, string, string, error) {
+	return api.SendMessageContext(context.Background(), channelID, MsgOptionUpdate(timestamp), MsgOptionCompose(options...))
 }
 
 // UpdateMessageContext updates a message in a channel
-func (api *Client) UpdateMessageContext(ctx context.Context, channelID, timestamp, text string) (string, string, string, error) {
-	return api.SendMessageContext(ctx, channelID, MsgOptionUpdate(timestamp), MsgOptionText(text, true))
+func (api *Client) UpdateMessageContext(ctx context.Context, channelID, timestamp string, options ...MsgOption) (string, string, string, error) {
+	return api.SendMessageContext(ctx, channelID, MsgOptionUpdate(timestamp), MsgOptionCompose(options...))
 }
 
 // SendMessage more flexible method for configuring messages.
@@ -165,7 +163,7 @@ func (api *Client) SendMessageContext(ctx context.Context, channelID string, opt
 		return "", "", "", err
 	}
 
-	if err = postForm(ctx, api.httpclient, config.endpoint, config.values, &response, api.debug); err != nil {
+	if err = postForm(ctx, api.httpclient, config.endpoint, config.values, &response, api); err != nil {
 		return "", "", "", err
 	}
 
@@ -182,7 +180,7 @@ func UnsafeApplyMsgOptions(token, channel string, options ...MsgOption) (string,
 
 func applyMsgOptions(token, channel string, options ...MsgOption) (sendConfig, error) {
 	config := sendConfig{
-		endpoint: SLACK_API + string(chatPostMessage),
+		endpoint: APIURL + string(chatPostMessage),
 		values: url.Values{
 			"token":   {token},
 			"channel": {channel},
@@ -219,26 +217,16 @@ type MsgOption func(*sendConfig) error
 // MsgOptionPost posts a messages, this is the default.
 func MsgOptionPost() MsgOption {
 	return func(config *sendConfig) error {
-		config.endpoint = SLACK_API + string(chatPostMessage)
-		config.values.Del("ts")
-		return nil
-	}
-}
-
-// MsgOptionPostEphemeral - DEPRECATED: use MsgOptionPostEphemeral2
-// posts an ephemeral message.
-func MsgOptionPostEphemeral() MsgOption {
-	return func(config *sendConfig) error {
-		config.endpoint = SLACK_API + string(chatPostEphemeral)
+		config.endpoint = APIURL + string(chatPostMessage)
 		config.values.Del("ts")
 		return nil
 	}
 }
 
-// MsgOptionPostEphemeral2 - posts an ephemeral message to the provided user.
-func MsgOptionPostEphemeral2(userID string) MsgOption {
+// MsgOptionPostEphemeral - posts an ephemeral message to the provided user.
+func MsgOptionPostEphemeral(userID string) MsgOption {
 	return func(config *sendConfig) error {
-		config.endpoint = SLACK_API + string(chatPostEphemeral)
+		config.endpoint = APIURL + string(chatPostEphemeral)
 		MsgOptionUser(userID)(config)
 		config.values.Del("ts")
 
@@ -249,7 +237,7 @@ func MsgOptionPostEphemeral2(userID string) MsgOption {
 // MsgOptionMeMessage posts a "me message" type from the calling user
 func MsgOptionMeMessage() MsgOption {
 	return func(config *sendConfig) error {
-		config.endpoint = SLACK_API + string(chatMeMessage)
+		config.endpoint = APIURL + string(chatMeMessage)
 		return nil
 	}
 }
@@ -257,7 +245,7 @@ func MsgOptionMeMessage() MsgOption {
 // MsgOptionUpdate updates a message based on the timestamp.
 func MsgOptionUpdate(timestamp string) MsgOption {
 	return func(config *sendConfig) error {
-		config.endpoint = SLACK_API + string(chatUpdate)
+		config.endpoint = APIURL + string(chatUpdate)
 		config.values.Add("ts", timestamp)
 		return nil
 	}
@@ -266,7 +254,7 @@ func MsgOptionUpdate(timestamp string) MsgOption {
 // MsgOptionDelete deletes a message based on the timestamp.
 func MsgOptionDelete(timestamp string) MsgOption {
 	return func(config *sendConfig) error {
-		config.endpoint = SLACK_API + string(chatDelete)
+		config.endpoint = APIURL + string(chatDelete)
 		config.values.Add("ts", timestamp)
 		return nil
 	}
@@ -365,7 +353,7 @@ func MsgOptionBroadcast() MsgOption {
 	}
 }
 
-// this function combines multiple options into a single option.
+// MsgOptionCompose combines multiple options into a single option.
 func MsgOptionCompose(options ...MsgOption) MsgOption {
 	return func(c *sendConfig) error {
 		for _, opt := range options {
@@ -377,6 +365,7 @@ func MsgOptionCompose(options ...MsgOption) MsgOption {
 	}
 }
 
+// MsgOptionParse set parse option.
 func MsgOptionParse(b bool) MsgOption {
 	return func(c *sendConfig) error {
 		var v string
diff --git a/chat_test.go b/chat_test.go
index fa7627659..90d391ba5 100644
--- a/chat_test.go
+++ b/chat_test.go
@@ -17,16 +17,16 @@ func postMessageInvalidChannelHandler(rw http.ResponseWriter, r *http.Request) {
 func TestPostMessageInvalidChannel(t *testing.T) {
 	http.HandleFunc("/chat.postMessage", postMessageInvalidChannelHandler)
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
-	_, _, err := api.PostMessage("CXXXXXXXX", "hello", PostMessageParameters{})
+	_, _, err := api.PostMessage("CXXXXXXXX", MsgOptionText("hello", false))
 	if err == nil {
-		t.Errorf("Expected error: %s; instead succeeded", "channel_not_found")
+		t.Errorf("Expected error: channel_not_found; instead succeeded")
 		return
 	}
 
 	if err.Error() != "channel_not_found" {
-		t.Errorf("Expected error: %s; received: %s", "channel_not_found", err)
+		t.Errorf("Expected error: channel_not_found; received: %s", err)
 		return
 	}
 }
diff --git a/conversation.go b/conversation.go
index 1c64116ef..940907a20 100644
--- a/conversation.go
+++ b/conversation.go
@@ -99,7 +99,7 @@ func (api *Client) GetUsersInConversationContext(ctx context.Context, params *Ge
 		ResponseMetaData responseMetaData `json:"response_metadata"`
 		SlackResponse
 	}{}
-	err := postSlackMethod(ctx, api.httpclient, "conversations.members", values, &response, api.debug)
+	err := postSlackMethod(ctx, api.httpclient, "conversations.members", values, &response, api)
 	if err != nil {
 		return nil, "", err
 	}
@@ -134,14 +134,12 @@ func (api *Client) GetConversationsForUserContext(ctx context.Context, params *G
 		ResponseMetaData responseMetaData `json:"response_metadata"`
 		SlackResponse
 	}{}
-	err = postSlackMethod(ctx, api.httpclient, "users.conversations", values, &response, api.debug)
+	err = postSlackMethod(ctx, api.httpclient, "users.conversations", values, &response, api)
 	if err != nil {
 		return nil, "", err
 	}
-	if !response.Ok {
-		return nil, "", errors.New(response.Error)
-	}
-	return response.Channels, response.ResponseMetaData.NextCursor, nil
+
+	return response.Channels, response.ResponseMetaData.NextCursor, response.Err()
 }
 
 // ArchiveConversation archives a conversation
@@ -156,7 +154,7 @@ func (api *Client) ArchiveConversationContext(ctx context.Context, channelID str
 		"channel": {channelID},
 	}
 	response := SlackResponse{}
-	err := postSlackMethod(ctx, api.httpclient, "conversations.archive", values, &response, api.debug)
+	err := postSlackMethod(ctx, api.httpclient, "conversations.archive", values, &response, api)
 	if err != nil {
 		return err
 	}
@@ -176,7 +174,7 @@ func (api *Client) UnArchiveConversationContext(ctx context.Context, channelID s
 		"channel": {channelID},
 	}
 	response := SlackResponse{}
-	err := postSlackMethod(ctx, api.httpclient, "conversations.unarchive", values, &response, api.debug)
+	err := postSlackMethod(ctx, api.httpclient, "conversations.unarchive", values, &response, api)
 	if err != nil {
 		return err
 	}
@@ -200,7 +198,7 @@ func (api *Client) SetTopicOfConversationContext(ctx context.Context, channelID,
 		SlackResponse
 		Channel *Channel `json:"channel"`
 	}{}
-	err := postSlackMethod(ctx, api.httpclient, "conversations.setTopic", values, &response, api.debug)
+	err := postSlackMethod(ctx, api.httpclient, "conversations.setTopic", values, &response, api)
 	if err != nil {
 		return nil, err
 	}
@@ -224,7 +222,7 @@ func (api *Client) SetPurposeOfConversationContext(ctx context.Context, channelI
 		SlackResponse
 		Channel *Channel `json:"channel"`
 	}{}
-	err := postSlackMethod(ctx, api.httpclient, "conversations.setPurpose", values, &response, api.debug)
+	err := postSlackMethod(ctx, api.httpclient, "conversations.setPurpose", values, &response, api)
 	if err != nil {
 		return nil, err
 	}
@@ -248,7 +246,7 @@ func (api *Client) RenameConversationContext(ctx context.Context, channelID, cha
 		SlackResponse
 		Channel *Channel `json:"channel"`
 	}{}
-	err := postSlackMethod(ctx, api.httpclient, "conversations.rename", values, &response, api.debug)
+	err := postSlackMethod(ctx, api.httpclient, "conversations.rename", values, &response, api)
 	if err != nil {
 		return nil, err
 	}
@@ -272,7 +270,7 @@ func (api *Client) InviteUsersToConversationContext(ctx context.Context, channel
 		SlackResponse
 		Channel *Channel `json:"channel"`
 	}{}
-	err := postSlackMethod(ctx, api.httpclient, "conversations.invite", values, &response, api.debug)
+	err := postSlackMethod(ctx, api.httpclient, "conversations.invite", values, &response, api)
 	if err != nil {
 		return nil, err
 	}
@@ -293,7 +291,7 @@ func (api *Client) KickUserFromConversationContext(ctx context.Context, channelI
 		"user":    {user},
 	}
 	response := SlackResponse{}
-	err := postSlackMethod(ctx, api.httpclient, "conversations.kick", values, &response, api.debug)
+	err := postSlackMethod(ctx, api.httpclient, "conversations.kick", values, &response, api)
 	if err != nil {
 		return err
 	}
@@ -318,7 +316,7 @@ func (api *Client) CloseConversationContext(ctx context.Context, channelID strin
 		AlreadyClosed bool `json:"already_closed"`
 	}{}
 
-	err = postSlackMethod(ctx, api.httpclient, "conversations.close", values, &response, api.debug)
+	err = postSlackMethod(ctx, api.httpclient, "conversations.close", values, &response, api)
 	if err != nil {
 		return false, false, err
 	}
@@ -339,7 +337,7 @@ func (api *Client) CreateConversationContext(ctx context.Context, channelName st
 		"is_private": {strconv.FormatBool(isPrivate)},
 	}
 	response, err := channelRequest(
-		ctx, api.httpclient, "conversations.create", values, api.debug)
+		ctx, api.httpclient, "conversations.create", values, api)
 	if err != nil {
 		return nil, err
 	}
@@ -360,7 +358,7 @@ func (api *Client) GetConversationInfoContext(ctx context.Context, channelID str
 		"include_locale": {strconv.FormatBool(includeLocale)},
 	}
 	response, err := channelRequest(
-		ctx, api.httpclient, "conversations.info", values, api.debug)
+		ctx, api.httpclient, "conversations.info", values, api)
 	if err != nil {
 		return nil, err
 	}
@@ -380,7 +378,7 @@ func (api *Client) LeaveConversationContext(ctx context.Context, channelID strin
 		"channel": {channelID},
 	}
 
-	response, err := channelRequest(ctx, api.httpclient, "conversations.leave", values, api.debug)
+	response, err := channelRequest(ctx, api.httpclient, "conversations.leave", values, api)
 	if err != nil {
 		return false, err
 	}
@@ -436,7 +434,7 @@ func (api *Client) GetConversationRepliesContext(ctx context.Context, params *Ge
 		Messages []Message `json:"messages"`
 	}{}
 
-	err = postSlackMethod(ctx, api.httpclient, "conversations.replies", values, &response, api.debug)
+	err = postSlackMethod(ctx, api.httpclient, "conversations.replies", values, &response, api)
 	if err != nil {
 		return nil, false, "", err
 	}
@@ -476,7 +474,7 @@ func (api *Client) GetConversationsContext(ctx context.Context, params *GetConve
 		ResponseMetaData responseMetaData `json:"response_metadata"`
 		SlackResponse
 	}{}
-	err = postSlackMethod(ctx, api.httpclient, "conversations.list", values, &response, api.debug)
+	err = postSlackMethod(ctx, api.httpclient, "conversations.list", values, &response, api)
 	if err != nil {
 		return nil, "", err
 	}
@@ -513,7 +511,7 @@ func (api *Client) OpenConversationContext(ctx context.Context, params *OpenConv
 		AlreadyOpen bool     `json:"already_open"`
 		SlackResponse
 	}{}
-	err := postSlackMethod(ctx, api.httpclient, "conversations.open", values, &response, api.debug)
+	err := postSlackMethod(ctx, api.httpclient, "conversations.open", values, &response, api)
 	if err != nil {
 		return nil, false, false, err
 	}
@@ -537,7 +535,7 @@ func (api *Client) JoinConversationContext(ctx context.Context, channelID string
 		} `json:"response_metadata"`
 		SlackResponse
 	}{}
-	err := postSlackMethod(ctx, api.httpclient, "conversations.join", values, &response, api.debug)
+	err := postSlackMethod(ctx, api.httpclient, "conversations.join", values, &response, api)
 	if err != nil {
 		return nil, "", nil, err
 	}
@@ -599,12 +597,10 @@ func (api *Client) GetConversationHistoryContext(ctx context.Context, params *Ge
 
 	response := GetConversationHistoryResponse{}
 
-	err := postSlackMethod(ctx, api.httpclient, "conversations.history", values, &response, api.debug)
+	err := postSlackMethod(ctx, api.httpclient, "conversations.history", values, &response, api)
 	if err != nil {
 		return nil, err
 	}
-	if !response.Ok {
-		return nil, errors.New(response.Error)
-	}
-	return &response, nil
+
+	return &response, response.Err()
 }
diff --git a/conversation_test.go b/conversation_test.go
index fe46ca767..109fec0ce 100644
--- a/conversation_test.go
+++ b/conversation_test.go
@@ -222,7 +222,7 @@ func getUsersInConversation(rw http.ResponseWriter, r *http.Request) {
 func TestGetUsersInConversation(t *testing.T) {
 	http.HandleFunc("/conversations.members", getUsersInConversation)
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	params := GetUsersInConversationParameters{
 		ChannelID: "CXXXXXXXX",
@@ -243,7 +243,7 @@ func TestGetUsersInConversation(t *testing.T) {
 func TestArchiveConversation(t *testing.T) {
 	http.HandleFunc("/conversations.archive", okJSONHandler)
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	err := api.ArchiveConversation("CXXXXXXXX")
 	if err != nil {
@@ -255,7 +255,7 @@ func TestArchiveConversation(t *testing.T) {
 func TestUnArchiveConversation(t *testing.T) {
 	http.HandleFunc("/conversations.unarchive", okJSONHandler)
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	err := api.UnArchiveConversation("CXXXXXXXX")
 	if err != nil {
@@ -291,7 +291,7 @@ func okChannelJsonHandler(rw http.ResponseWriter, r *http.Request) {
 func TestSetTopicOfConversation(t *testing.T) {
 	http.HandleFunc("/conversations.setTopic", okChannelJsonHandler)
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	inputChannel := getTestChannel()
 	channel, err := api.SetTopicOfConversation("CXXXXXXXX", inputChannel.Topic.Value)
@@ -307,7 +307,7 @@ func TestSetTopicOfConversation(t *testing.T) {
 func TestSetPurposeOfConversation(t *testing.T) {
 	http.HandleFunc("/conversations.setPurpose", okChannelJsonHandler)
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	inputChannel := getTestChannel()
 	channel, err := api.SetPurposeOfConversation("CXXXXXXXX", inputChannel.Purpose.Value)
@@ -323,7 +323,7 @@ func TestSetPurposeOfConversation(t *testing.T) {
 func TestRenameConversation(t *testing.T) {
 	http.HandleFunc("/conversations.rename", okChannelJsonHandler)
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	inputChannel := getTestChannel()
 	channel, err := api.RenameConversation("CXXXXXXXX", inputChannel.Name)
@@ -339,7 +339,7 @@ func TestRenameConversation(t *testing.T) {
 func TestInviteUsersToConversation(t *testing.T) {
 	http.HandleFunc("/conversations.invite", okChannelJsonHandler)
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	users := []string{"UXXXXXXX1", "UXXXXXXX2"}
 	channel, err := api.InviteUsersToConversation("CXXXXXXXX", users...)
@@ -356,7 +356,7 @@ func TestInviteUsersToConversation(t *testing.T) {
 func TestKickUserFromConversation(t *testing.T) {
 	http.HandleFunc("/conversations.kick", okJSONHandler)
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	err := api.KickUserFromConversation("CXXXXXXXX", "UXXXXXXXX")
 	if err != nil {
@@ -379,7 +379,7 @@ func closeConversationHandler(rw http.ResponseWriter, r *http.Request) {
 func TestCloseConversation(t *testing.T) {
 	http.HandleFunc("/conversations.close", closeConversationHandler)
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	_, _, err := api.CloseConversation("CXXXXXXXX")
 	if err != nil {
@@ -391,7 +391,7 @@ func TestCloseConversation(t *testing.T) {
 func TestCreateConversation(t *testing.T) {
 	http.HandleFunc("/conversations.create", okChannelJsonHandler)
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	channel, err := api.CreateConversation("CXXXXXXXX", false)
 	if err != nil {
@@ -407,7 +407,7 @@ func TestCreateConversation(t *testing.T) {
 func TestGetConversationInfo(t *testing.T) {
 	http.HandleFunc("/conversations.info", okChannelJsonHandler)
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	channel, err := api.GetConversationInfo("CXXXXXXXX", false)
 	if err != nil {
@@ -433,7 +433,7 @@ func leaveConversationHandler(rw http.ResponseWriter, r *http.Request) {
 func TestLeaveConversation(t *testing.T) {
 	http.HandleFunc("/conversations.leave", leaveConversationHandler)
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	_, err := api.LeaveConversation("CXXXXXXXX")
 	if err != nil {
@@ -460,7 +460,7 @@ func getConversationRepliesHander(rw http.ResponseWriter, r *http.Request) {
 func TestGetConversationReplies(t *testing.T) {
 	http.HandleFunc("/conversations.replies", getConversationRepliesHander)
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	params := GetConversationRepliesParameters{
 		ChannelID: "CXXXXXXXX",
@@ -490,7 +490,7 @@ func getConversationsHander(rw http.ResponseWriter, r *http.Request) {
 func TestGetConversations(t *testing.T) {
 	http.HandleFunc("/conversations.list", getConversationsHander)
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	params := GetConversationsParameters{}
 	_, _, err := api.GetConversations(&params)
@@ -515,7 +515,7 @@ func openConversationHandler(rw http.ResponseWriter, r *http.Request) {
 func TestOpenConversation(t *testing.T) {
 	http.HandleFunc("/conversations.open", openConversationHandler)
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	params := OpenConversationParameters{ChannelID: "CXXXXXXXX"}
 	_, _, _, err := api.OpenConversation(&params)
@@ -542,7 +542,7 @@ func joinConversationHandler(rw http.ResponseWriter, r *http.Request) {
 func TestJoinConversation(t *testing.T) {
 	http.HandleFunc("/conversations.join", joinConversationHandler)
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	_, _, _, err := api.JoinConversation("CXXXXXXXX")
 	if err != nil {
@@ -561,7 +561,7 @@ func getConversationHistoryHandler(rw http.ResponseWriter, r *http.Request) {
 func TestGetConversationHistory(t *testing.T) {
 	http.HandleFunc("/conversations.history", getConversationHistoryHandler)
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	params := GetConversationHistoryParameters{ChannelID: "CXXXXXXXX"}
 	_, err := api.GetConversationHistory(&params)
diff --git a/dialog.go b/dialog.go
index d1435d54c..914e01bee 100644
--- a/dialog.go
+++ b/dialog.go
@@ -108,8 +108,8 @@ func (api *Client) OpenDialogContext(ctx context.Context, triggerID string, dial
 	}
 
 	response := &DialogOpenResponse{}
-	endpoint := SLACK_API + "dialog.open"
-	if err := postJSON(ctx, api.httpclient, endpoint, api.token, encoded, response, api.debug); err != nil {
+	endpoint := APIURL + "dialog.open"
+	if err := postJSON(ctx, api.httpclient, endpoint, api.token, encoded, response, api); err != nil {
 		return err
 	}
 
diff --git a/dialog_test.go b/dialog_test.go
index 5367d8bb7..1c7538c36 100644
--- a/dialog_test.go
+++ b/dialog_test.go
@@ -286,7 +286,7 @@ func openDialogHandler(rw http.ResponseWriter, r *http.Request) {
 func TestOpenDialog(t *testing.T) {
 	http.HandleFunc("/dialog.open", openDialogHandler)
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	dialog, err := unmarshalDialog()
 	if err != nil {
diff --git a/dnd.go b/dnd.go
index 26d36d6ae..da6e4a16d 100644
--- a/dnd.go
+++ b/dnd.go
@@ -36,9 +36,9 @@ type dndTeamInfoResponse struct {
 	SlackResponse
 }
 
-func dndRequest(ctx context.Context, client HTTPRequester, path string, values url.Values, debug bool) (*dndResponseFull, error) {
+func dndRequest(ctx context.Context, client httpClient, path string, values url.Values, d debug) (*dndResponseFull, error) {
 	response := &dndResponseFull{}
-	err := postSlackMethod(ctx, client, path, values, response, debug)
+	err := postSlackMethod(ctx, client, path, values, response, d)
 	if err != nil {
 		return nil, err
 	}
@@ -61,7 +61,7 @@ func (api *Client) EndDNDContext(ctx context.Context) error {
 
 	response := &SlackResponse{}
 
-	if err := postSlackMethod(ctx, api.httpclient, "dnd.endDnd", values, response, api.debug); err != nil {
+	if err := postSlackMethod(ctx, api.httpclient, "dnd.endDnd", values, response, api); err != nil {
 		return err
 	}
 
@@ -79,7 +79,7 @@ func (api *Client) EndSnoozeContext(ctx context.Context) (*DNDStatus, error) {
 		"token": {api.token},
 	}
 
-	response, err := dndRequest(ctx, api.httpclient, "dnd.endSnooze", values, api.debug)
+	response, err := dndRequest(ctx, api.httpclient, "dnd.endSnooze", values, api)
 	if err != nil {
 		return nil, err
 	}
@@ -100,7 +100,7 @@ func (api *Client) GetDNDInfoContext(ctx context.Context, user *string) (*DNDSta
 		values.Set("user", *user)
 	}
 
-	response, err := dndRequest(ctx, api.httpclient, "dnd.info", values, api.debug)
+	response, err := dndRequest(ctx, api.httpclient, "dnd.info", values, api)
 	if err != nil {
 		return nil, err
 	}
@@ -120,11 +120,12 @@ func (api *Client) GetDNDTeamInfoContext(ctx context.Context, users []string) (m
 	}
 	response := &dndTeamInfoResponse{}
 
-	if err := postSlackMethod(ctx, api.httpclient, "dnd.teamInfo", values, response, api.debug); err != nil {
+	if err := postSlackMethod(ctx, api.httpclient, "dnd.teamInfo", values, response, api); err != nil {
 		return nil, err
 	}
-	if !response.Ok {
-		return nil, errors.New(response.Error)
+
+	if response.Err() != nil {
+		return nil, response.Err()
 	}
 	return response.Users, nil
 }
@@ -144,7 +145,7 @@ func (api *Client) SetSnoozeContext(ctx context.Context, minutes int) (*DNDStatu
 		"num_minutes": {strconv.Itoa(minutes)},
 	}
 
-	response, err := dndRequest(ctx, api.httpclient, "dnd.setSnooze", values, api.debug)
+	response, err := dndRequest(ctx, api.httpclient, "dnd.setSnooze", values, api)
 	if err != nil {
 		return nil, err
 	}
diff --git a/dnd_test.go b/dnd_test.go
index ddcce8fb3..74ec94f42 100644
--- a/dnd_test.go
+++ b/dnd_test.go
@@ -12,7 +12,7 @@ func TestSlack_EndDND(t *testing.T) {
 		w.Write([]byte(`{ "ok": true }`))
 	})
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	err := api.EndDND()
 	if err != nil {
@@ -36,7 +36,7 @@ func TestSlack_EndSnooze(t *testing.T) {
 		SnoozeInfo:         SnoozeInfo{SnoozeEnabled: false},
 	}
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	snoozeState, err := api.EndSnooze()
 	if err != nil {
@@ -72,7 +72,7 @@ func TestSlack_GetDNDInfo(t *testing.T) {
 		},
 	}
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	userDNDInfoResponse, err := api.GetDNDInfo(nil)
 	if err != nil {
@@ -116,7 +116,7 @@ func TestSlack_GetDNDTeamInfo(t *testing.T) {
 		},
 	}
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	usersDNDInfoResponse, err := api.GetDNDTeamInfo(nil)
 	if err != nil {
@@ -146,7 +146,7 @@ func TestSlack_SetSnooze(t *testing.T) {
 		},
 	}
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	snoozeResponse, err := api.SetSnooze(60)
 	if err != nil {
diff --git a/emoji.go b/emoji.go
index fe2945c49..aed2129fd 100644
--- a/emoji.go
+++ b/emoji.go
@@ -23,7 +23,7 @@ func (api *Client) GetEmojiContext(ctx context.Context) (map[string]string, erro
 	}
 	response := &emojiResponseFull{}
 
-	err := postSlackMethod(ctx, api.httpclient, "emoji.list", values, response, api.debug)
+	err := postSlackMethod(ctx, api.httpclient, "emoji.list", values, response, api)
 	if err != nil {
 		return nil, err
 	}
diff --git a/emoji_test.go b/emoji_test.go
index 1aa086da1..f3924a73a 100644
--- a/emoji_test.go
+++ b/emoji_test.go
@@ -20,7 +20,7 @@ func TestGetEmoji(t *testing.T) {
 	http.HandleFunc("/emoji.list", getEmojiHandler)
 
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	emojisResponse := map[string]string{
 		"bowtie":   "https://my.slack.com/emoji/bowtie/46ec6f2bb0.png",
diff --git a/examples/eventsapi/events.go b/examples/eventsapi/events.go
index a96edfda4..aac8d2c4d 100644
--- a/examples/eventsapi/events.go
+++ b/examples/eventsapi/events.go
@@ -18,7 +18,7 @@ func main() {
 		buf := new(bytes.Buffer)
 		buf.ReadFrom(r.Body)
 		body := buf.String()
-		eventsAPIEvent, e := slackevents.ParseEvent(json.RawMessage(body), slackevents.OptionVerifyToken(&slackevents.TokenComparator{"TOKEN"}))
+		eventsAPIEvent, e := slackevents.ParseEvent(json.RawMessage(body), slackevents.OptionVerifyToken(&slackevents.TokenComparator{VerificationToken: "TOKEN"}))
 		if e != nil {
 			w.WriteHeader(http.StatusInternalServerError)
 		}
@@ -33,11 +33,10 @@ func main() {
 			w.Write([]byte(r.Challenge))
 		}
 		if eventsAPIEvent.Type == slackevents.CallbackEvent {
-			postParams := slack.PostMessageParameters{}
 			innerEvent := eventsAPIEvent.InnerEvent
 			switch ev := innerEvent.Data.(type) {
 			case *slackevents.AppMentionEvent:
-				api.PostMessage(ev.Channel, "Yes, hello.", postParams)
+				api.PostMessage(ev.Channel, slack.MsgOptionText("Yes, hello.", false))
 			}
 		}
 	})
diff --git a/examples/ims/ims.go b/examples/ims/ims.go
index 80d73c0a6..f8ee814d1 100644
--- a/examples/ims/ims.go
+++ b/examples/ims/ims.go
@@ -17,5 +17,5 @@ func main() {
 		fmt.Printf("%s\n", err)
 	}
 
-	api.PostMessage(channelID, "Hello World!", slack.PostMessageParameters{})
+	api.PostMessage(channelID, slack.MsgOptionText("Hello World!", false))
 }
diff --git a/examples/messages/messages.go b/examples/messages/messages.go
index b3ea87f30..f97474298 100644
--- a/examples/messages/messages.go
+++ b/examples/messages/messages.go
@@ -8,7 +8,6 @@ import (
 
 func main() {
 	api := slack.New("YOUR_TOKEN_HERE")
-	params := slack.PostMessageParameters{}
 	attachment := slack.Attachment{
 		Pretext: "some pretext",
 		Text:    "some text",
@@ -22,8 +21,8 @@ func main() {
 			},
 		*/
 	}
-	params.Attachments = []slack.Attachment{attachment}
-	channelID, timestamp, err := api.PostMessage("CHANNEL_ID", "Some text", params)
+
+	channelID, timestamp, err := api.PostMessage("CHANNEL_ID", slack.MsgOptionText("Some text", false), slack.MsgOptionAttachments(attachment))
 	if err != nil {
 		fmt.Printf("%s\n", err)
 		return
diff --git a/examples/pins/pins.go b/examples/pins/pins.go
index d225184c8..74876f953 100644
--- a/examples/pins/pins.go
+++ b/examples/pins/pins.go
@@ -20,15 +20,13 @@ func main() {
 	flag.BoolVar(&debug, "debug", false, "Show JSON output")
 	flag.Parse()
 
-	api := slack.New(apiToken)
-	if debug {
-		api.SetDebug(true)
-	}
+	api := slack.New(apiToken, slack.OptionDebug(debug))
 
 	var (
 		postAsUserName  string
 		postAsUserID    string
 		postToChannelID string
+		channels        []slack.Channel
 	)
 
 	// Find the user to post as.
@@ -51,8 +49,7 @@ func main() {
 		// If the channel exists, that means we just need to unarchive it
 		if err.Error() == "name_taken" {
 			err = nil
-			channels, err := api.GetChannels(false)
-			if err != nil {
+			if channels, err = api.GetChannels(false); err != nil {
 				fmt.Println("Could not retrieve channels")
 				return
 			}
@@ -80,8 +77,7 @@ func main() {
 	fmt.Printf("Posting as %s (%s) in channel %s\n", postAsUserName, postAsUserID, postToChannelID)
 
 	// Post a message.
-	postParams := slack.PostMessageParameters{}
-	channelID, timestamp, err := api.PostMessage(postToChannelID, "Is this any good?", postParams)
+	channelID, timestamp, err := api.PostMessage(postToChannelID, slack.MsgOptionText("Is this any good?", false))
 	if err != nil {
 		fmt.Printf("Error posting message: %s\n", err)
 		return
@@ -91,7 +87,7 @@ func main() {
 	msgRef := slack.NewRefToMessage(channelID, timestamp)
 
 	// Add message pin to channel
-	if err := api.AddPin(channelID, msgRef); err != nil {
+	if err = api.AddPin(channelID, msgRef); err != nil {
 		fmt.Printf("Error adding pin: %s\n", err)
 		return
 	}
diff --git a/examples/reactions/reactions.go b/examples/reactions/reactions.go
index 753f0d258..47808ff3a 100644
--- a/examples/reactions/reactions.go
+++ b/examples/reactions/reactions.go
@@ -17,10 +17,7 @@ func main() {
 	flag.BoolVar(&debug, "debug", false, "Show JSON output")
 	flag.Parse()
 
-	api := slack.New(apiToken)
-	if debug {
-		api.SetDebug(true)
-	}
+	api := slack.New(apiToken, slack.OptionDebug(debug))
 
 	var (
 		postAsUserName  string
@@ -56,8 +53,7 @@ func main() {
 	fmt.Printf("Posting as %s (%s) in DM with %s (%s), channel %s\n", postAsUserName, postAsUserID, postToUserName, postToUserID, postToChannelID)
 
 	// Post a message.
-	postParams := slack.PostMessageParameters{}
-	channelID, timestamp, err := api.PostMessage(postToChannelID, "Is this any good?", postParams)
+	channelID, timestamp, err := api.PostMessage(postToChannelID, slack.MsgOptionText("Is this any good?", false))
 	if err != nil {
 		fmt.Printf("Error posting message: %s\n", err)
 		return
@@ -67,13 +63,13 @@ func main() {
 	msgRef := slack.NewRefToMessage(channelID, timestamp)
 
 	// React with :+1:
-	if err := api.AddReaction("+1", msgRef); err != nil {
+	if err = api.AddReaction("+1", msgRef); err != nil {
 		fmt.Printf("Error adding reaction: %s\n", err)
 		return
 	}
 
 	// React with :-1:
-	if err := api.AddReaction("cry", msgRef); err != nil {
+	if err = api.AddReaction("cry", msgRef); err != nil {
 		fmt.Printf("Error adding reaction: %s\n", err)
 		return
 	}
diff --git a/examples/stars/stars.go b/examples/stars/stars.go
index d20c3dcfa..c22fa0853 100644
--- a/examples/stars/stars.go
+++ b/examples/stars/stars.go
@@ -17,10 +17,7 @@ func main() {
 	flag.BoolVar(&debug, "debug", false, "Show JSON output")
 	flag.Parse()
 
-	api := slack.New(apiToken)
-	if debug {
-		api.SetDebug(true)
-	}
+	api := slack.New(apiToken, slack.OptionDebug(debug))
 
 	// Get all stars for the usr.
 	params := slack.NewStarsParameters()
diff --git a/examples/websocket/websocket.go b/examples/websocket/websocket.go
index c232951a4..9dafefd5d 100644
--- a/examples/websocket/websocket.go
+++ b/examples/websocket/websocket.go
@@ -9,10 +9,11 @@ import (
 )
 
 func main() {
-	api := slack.New("YOUR TOKEN HERE")
-	logger := log.New(os.Stdout, "slack-bot: ", log.Lshortfile|log.LstdFlags)
-	slack.SetLogger(logger)
-	api.SetDebug(true)
+	api := slack.New(
+		"YOUR TOKEN HERE",
+		slack.OptionDebug(true),
+		slack.OptionLog(log.New(os.Stdout, "slack-bot: ", log.Lshortfile|log.LstdFlags)),
+	)
 
 	rtm := api.NewRTM()
 	go rtm.ManageConnection()
diff --git a/files.go b/files.go
index 0550c9fb5..13158582d 100644
--- a/files.go
+++ b/files.go
@@ -137,16 +137,14 @@ func NewGetFilesParameters() GetFilesParameters {
 	}
 }
 
-func fileRequest(ctx context.Context, client HTTPRequester, path string, values url.Values, debug bool) (*fileResponseFull, error) {
+func fileRequest(ctx context.Context, client httpClient, path string, values url.Values, d debug) (*fileResponseFull, error) {
 	response := &fileResponseFull{}
-	err := postForm(ctx, client, SLACK_API+path, values, response, debug)
+	err := postForm(ctx, client, APIURL+path, values, response, d)
 	if err != nil {
 		return nil, err
 	}
-	if !response.Ok {
-		return nil, errors.New(response.Error)
-	}
-	return response, nil
+
+	return response, response.Err()
 }
 
 // GetFileInfo retrieves a file and related comments
@@ -163,7 +161,7 @@ func (api *Client) GetFileInfoContext(ctx context.Context, fileID string, count,
 		"page":  {strconv.Itoa(page)},
 	}
 
-	response, err := fileRequest(ctx, api.httpclient, "files.info", values, api.debug)
+	response, err := fileRequest(ctx, api.httpclient, "files.info", values, api)
 	if err != nil {
 		return nil, nil, nil, err
 	}
@@ -202,7 +200,7 @@ func (api *Client) GetFilesContext(ctx context.Context, params GetFilesParameter
 		values.Add("page", strconv.Itoa(params.Page))
 	}
 
-	response, err := fileRequest(ctx, api.httpclient, "files.list", values, api.debug)
+	response, err := fileRequest(ctx, api.httpclient, "files.list", values, api)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -246,19 +244,17 @@ func (api *Client) UploadFileContext(ctx context.Context, params FileUploadParam
 	}
 	if params.Content != "" {
 		values.Add("content", params.Content)
-		err = postForm(ctx, api.httpclient, SLACK_API+"files.upload", values, response, api.debug)
+		err = postForm(ctx, api.httpclient, APIURL+"files.upload", values, response, api)
 	} else if params.File != "" {
-		err = postLocalWithMultipartResponse(ctx, api.httpclient, "files.upload", params.File, "file", values, response, api.debug)
+		err = postLocalWithMultipartResponse(ctx, api.httpclient, "files.upload", params.File, "file", values, response, api)
 	} else if params.Reader != nil {
-		err = postWithMultipartResponse(ctx, api.httpclient, "files.upload", params.Filename, "file", values, params.Reader, response, api.debug)
+		err = postWithMultipartResponse(ctx, api.httpclient, "files.upload", params.Filename, "file", values, params.Reader, response, api)
 	}
 	if err != nil {
 		return nil, err
 	}
-	if !response.Ok {
-		return nil, errors.New(response.Error)
-	}
-	return &response.File, nil
+
+	return &response.File, response.Err()
 }
 
 // DeleteFileComment deletes a file's comment
@@ -277,7 +273,7 @@ func (api *Client) DeleteFileCommentContext(ctx context.Context, fileID, comment
 		"file":  {fileID},
 		"id":    {commentID},
 	}
-	_, err = fileRequest(ctx, api.httpclient, "files.comments.delete", values, api.debug)
+	_, err = fileRequest(ctx, api.httpclient, "files.comments.delete", values, api)
 	return err
 }
 
@@ -293,7 +289,7 @@ func (api *Client) DeleteFileContext(ctx context.Context, fileID string) (err er
 		"file":  {fileID},
 	}
 
-	_, err = fileRequest(ctx, api.httpclient, "files.delete", values, api.debug)
+	_, err = fileRequest(ctx, api.httpclient, "files.delete", values, api)
 	return err
 }
 
@@ -309,7 +305,7 @@ func (api *Client) RevokeFilePublicURLContext(ctx context.Context, fileID string
 		"file":  {fileID},
 	}
 
-	response, err := fileRequest(ctx, api.httpclient, "files.revokePublicURL", values, api.debug)
+	response, err := fileRequest(ctx, api.httpclient, "files.revokePublicURL", values, api)
 	if err != nil {
 		return nil, err
 	}
@@ -328,7 +324,7 @@ func (api *Client) ShareFilePublicURLContext(ctx context.Context, fileID string)
 		"file":  {fileID},
 	}
 
-	response, err := fileRequest(ctx, api.httpclient, "files.sharedPublicURL", values, api.debug)
+	response, err := fileRequest(ctx, api.httpclient, "files.sharedPublicURL", values, api)
 	if err != nil {
 		return nil, nil, nil, err
 	}
diff --git a/files_test.go b/files_test.go
index 91d6e8e1f..975e39b86 100644
--- a/files_test.go
+++ b/files_test.go
@@ -41,7 +41,7 @@ func (h *fileCommentHandler) handler(w http.ResponseWriter, r *http.Request) {
 
 func TestSlack_DeleteFileComment(t *testing.T) {
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	tests := []struct {
 		title       string
@@ -125,7 +125,7 @@ func TestUploadFile(t *testing.T) {
 	http.HandleFunc("/auth.test", authTestHandler)
 	http.HandleFunc("/files.upload", uploadFileHandler)
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	params := FileUploadParameters{
 		Filename: "test.txt", Content: "test content",
diff --git a/groups.go b/groups.go
index 67e78e993..a248f6fd9 100644
--- a/groups.go
+++ b/groups.go
@@ -2,7 +2,6 @@ package slack
 
 import (
 	"context"
-	"errors"
 	"net/url"
 	"strconv"
 )
@@ -28,16 +27,14 @@ type groupResponseFull struct {
 	SlackResponse
 }
 
-func groupRequest(ctx context.Context, client HTTPRequester, path string, values url.Values, debug bool) (*groupResponseFull, error) {
+func groupRequest(ctx context.Context, client httpClient, path string, values url.Values, d debug) (*groupResponseFull, error) {
 	response := &groupResponseFull{}
-	err := postForm(ctx, client, SLACK_API+path, values, response, debug)
+	err := postForm(ctx, client, APIURL+path, values, response, d)
 	if err != nil {
 		return nil, err
 	}
-	if !response.Ok {
-		return nil, errors.New(response.Error)
-	}
-	return response, nil
+
+	return response, response.Err()
 }
 
 // ArchiveGroup archives a private group
@@ -52,7 +49,7 @@ func (api *Client) ArchiveGroupContext(ctx context.Context, group string) error
 		"channel": {group},
 	}
 
-	_, err := groupRequest(ctx, api.httpclient, "groups.archive", values, api.debug)
+	_, err := groupRequest(ctx, api.httpclient, "groups.archive", values, api)
 	return err
 }
 
@@ -68,7 +65,7 @@ func (api *Client) UnarchiveGroupContext(ctx context.Context, group string) erro
 		"channel": {group},
 	}
 
-	_, err := groupRequest(ctx, api.httpclient, "groups.unarchive", values, api.debug)
+	_, err := groupRequest(ctx, api.httpclient, "groups.unarchive", values, api)
 	return err
 }
 
@@ -84,7 +81,7 @@ func (api *Client) CreateGroupContext(ctx context.Context, group string) (*Group
 		"name":  {group},
 	}
 
-	response, err := groupRequest(ctx, api.httpclient, "groups.create", values, api.debug)
+	response, err := groupRequest(ctx, api.httpclient, "groups.create", values, api)
 	if err != nil {
 		return nil, err
 	}
@@ -109,7 +106,7 @@ func (api *Client) CreateChildGroupContext(ctx context.Context, group string) (*
 		"channel": {group},
 	}
 
-	response, err := groupRequest(ctx, api.httpclient, "groups.createChild", values, api.debug)
+	response, err := groupRequest(ctx, api.httpclient, "groups.createChild", values, api)
 	if err != nil {
 		return nil, err
 	}
@@ -128,7 +125,7 @@ func (api *Client) CloseGroupContext(ctx context.Context, group string) (bool, b
 		"channel": {group},
 	}
 
-	response, err := imRequest(ctx, api.httpclient, "groups.close", values, api.debug)
+	response, err := imRequest(ctx, api.httpclient, "groups.close", values, api)
 	if err != nil {
 		return false, false, err
 	}
@@ -170,7 +167,7 @@ func (api *Client) GetGroupHistoryContext(ctx context.Context, group string, par
 		}
 	}
 
-	response, err := groupRequest(ctx, api.httpclient, "groups.history", values, api.debug)
+	response, err := groupRequest(ctx, api.httpclient, "groups.history", values, api)
 	if err != nil {
 		return nil, err
 	}
@@ -190,7 +187,7 @@ func (api *Client) InviteUserToGroupContext(ctx context.Context, group, user str
 		"user":    {user},
 	}
 
-	response, err := groupRequest(ctx, api.httpclient, "groups.invite", values, api.debug)
+	response, err := groupRequest(ctx, api.httpclient, "groups.invite", values, api)
 	if err != nil {
 		return nil, false, err
 	}
@@ -209,7 +206,7 @@ func (api *Client) LeaveGroupContext(ctx context.Context, group string) (err err
 		"channel": {group},
 	}
 
-	_, err = groupRequest(ctx, api.httpclient, "groups.leave", values, api.debug)
+	_, err = groupRequest(ctx, api.httpclient, "groups.leave", values, api)
 	return err
 }
 
@@ -226,7 +223,7 @@ func (api *Client) KickUserFromGroupContext(ctx context.Context, group, user str
 		"user":    {user},
 	}
 
-	_, err = groupRequest(ctx, api.httpclient, "groups.kick", values, api.debug)
+	_, err = groupRequest(ctx, api.httpclient, "groups.kick", values, api)
 	return err
 }
 
@@ -244,7 +241,7 @@ func (api *Client) GetGroupsContext(ctx context.Context, excludeArchived bool) (
 		values.Add("exclude_archived", "1")
 	}
 
-	response, err := groupRequest(ctx, api.httpclient, "groups.list", values, api.debug)
+	response, err := groupRequest(ctx, api.httpclient, "groups.list", values, api)
 	if err != nil {
 		return nil, err
 	}
@@ -263,7 +260,7 @@ func (api *Client) GetGroupInfoContext(ctx context.Context, group string) (*Grou
 		"channel": {group},
 	}
 
-	response, err := groupRequest(ctx, api.httpclient, "groups.info", values, api.debug)
+	response, err := groupRequest(ctx, api.httpclient, "groups.info", values, api)
 	if err != nil {
 		return nil, err
 	}
@@ -288,7 +285,7 @@ func (api *Client) SetGroupReadMarkContext(ctx context.Context, group, ts string
 		"ts":      {ts},
 	}
 
-	_, err = groupRequest(ctx, api.httpclient, "groups.mark", values, api.debug)
+	_, err = groupRequest(ctx, api.httpclient, "groups.mark", values, api)
 	return err
 }
 
@@ -304,7 +301,7 @@ func (api *Client) OpenGroupContext(ctx context.Context, group string) (bool, bo
 		"channel": {group},
 	}
 
-	response, err := groupRequest(ctx, api.httpclient, "groups.open", values, api.debug)
+	response, err := groupRequest(ctx, api.httpclient, "groups.open", values, api)
 	if err != nil {
 		return false, false, err
 	}
@@ -328,7 +325,7 @@ func (api *Client) RenameGroupContext(ctx context.Context, group, name string) (
 
 	// XXX: the created entry in this call returns a string instead of a number
 	// so I may have to do some workaround to solve it.
-	response, err := groupRequest(ctx, api.httpclient, "groups.rename", values, api.debug)
+	response, err := groupRequest(ctx, api.httpclient, "groups.rename", values, api)
 	if err != nil {
 		return nil, err
 	}
@@ -348,7 +345,7 @@ func (api *Client) SetGroupPurposeContext(ctx context.Context, group, purpose st
 		"purpose": {purpose},
 	}
 
-	response, err := groupRequest(ctx, api.httpclient, "groups.setPurpose", values, api.debug)
+	response, err := groupRequest(ctx, api.httpclient, "groups.setPurpose", values, api)
 	if err != nil {
 		return "", err
 	}
@@ -368,7 +365,7 @@ func (api *Client) SetGroupTopicContext(ctx context.Context, group, topic string
 		"topic":   {topic},
 	}
 
-	response, err := groupRequest(ctx, api.httpclient, "groups.setTopic", values, api.debug)
+	response, err := groupRequest(ctx, api.httpclient, "groups.setTopic", values, api)
 	if err != nil {
 		return "", err
 	}
diff --git a/im.go b/im.go
index fa8b09593..10563d91c 100644
--- a/im.go
+++ b/im.go
@@ -2,7 +2,6 @@ package slack
 
 import (
 	"context"
-	"errors"
 	"net/url"
 	"strconv"
 )
@@ -29,16 +28,14 @@ type IM struct {
 	IsUserDeleted bool   `json:"is_user_deleted"`
 }
 
-func imRequest(ctx context.Context, client HTTPRequester, path string, values url.Values, debug bool) (*imResponseFull, error) {
+func imRequest(ctx context.Context, client httpClient, path string, values url.Values, d debug) (*imResponseFull, error) {
 	response := &imResponseFull{}
-	err := postSlackMethod(ctx, client, path, values, response, debug)
+	err := postSlackMethod(ctx, client, path, values, response, d)
 	if err != nil {
 		return nil, err
 	}
-	if !response.Ok {
-		return nil, errors.New(response.Error)
-	}
-	return response, nil
+
+	return response, response.Err()
 }
 
 // CloseIMChannel closes the direct message channel
@@ -53,7 +50,7 @@ func (api *Client) CloseIMChannelContext(ctx context.Context, channel string) (b
 		"channel": {channel},
 	}
 
-	response, err := imRequest(ctx, api.httpclient, "im.close", values, api.debug)
+	response, err := imRequest(ctx, api.httpclient, "im.close", values, api)
 	if err != nil {
 		return false, false, err
 	}
@@ -74,7 +71,7 @@ func (api *Client) OpenIMChannelContext(ctx context.Context, user string) (bool,
 		"user":  {user},
 	}
 
-	response, err := imRequest(ctx, api.httpclient, "im.open", values, api.debug)
+	response, err := imRequest(ctx, api.httpclient, "im.open", values, api)
 	if err != nil {
 		return false, false, "", err
 	}
@@ -94,7 +91,7 @@ func (api *Client) MarkIMChannelContext(ctx context.Context, channel, ts string)
 		"ts":      {ts},
 	}
 
-	_, err := imRequest(ctx, api.httpclient, "im.mark", values, api.debug)
+	_, err := imRequest(ctx, api.httpclient, "im.mark", values, api)
 	return err
 }
 
@@ -133,7 +130,7 @@ func (api *Client) GetIMHistoryContext(ctx context.Context, channel string, para
 		}
 	}
 
-	response, err := imRequest(ctx, api.httpclient, "im.history", values, api.debug)
+	response, err := imRequest(ctx, api.httpclient, "im.history", values, api)
 	if err != nil {
 		return nil, err
 	}
@@ -151,7 +148,7 @@ func (api *Client) GetIMChannelsContext(ctx context.Context) ([]IM, error) {
 		"token": {api.token},
 	}
 
-	response, err := imRequest(ctx, api.httpclient, "im.list", values, api.debug)
+	response, err := imRequest(ctx, api.httpclient, "im.list", values, api)
 	if err != nil {
 		return nil, err
 	}
diff --git a/logger.go b/logger.go
index 501d1672d..e494a98f6 100644
--- a/logger.go
+++ b/logger.go
@@ -2,20 +2,6 @@ package slack
 
 import (
 	"fmt"
-	"sync"
-)
-
-// SetLogger let's library users supply a logger, so that api debugging
-// can be logged along with the application's debugging info.
-func SetLogger(l logProvider) {
-	loggerMutex.Lock()
-	logger = ilogger{logProvider: l}
-	loggerMutex.Unlock()
-}
-
-var (
-	loggerMutex = new(sync.Mutex)
-	logger      logInternal // A logger that can be set by consumers
 )
 
 // logProvider is a logger interface compatible with both stdlib and some
@@ -32,6 +18,15 @@ type logInternal interface {
 	Output(int, string) error
 }
 
+type debug interface {
+	Debug() bool
+
+	// Debugf print a formatted debug line.
+	Debugf(format string, v ...interface{})
+	// Debugln print a debug line.
+	Debugln(v ...interface{})
+}
+
 // ilogger implements the additional methods used by our internal logging.
 type ilogger struct {
 	logProvider
@@ -51,3 +46,15 @@ func (t ilogger) Printf(format string, v ...interface{}) {
 func (t ilogger) Print(v ...interface{}) {
 	t.Output(2, fmt.Sprint(v...))
 }
+
+type discard struct{}
+
+func (t discard) Debug() bool {
+	return false
+}
+
+// Debugf print a formatted debug line.
+func (t discard) Debugf(format string, v ...interface{}) {}
+
+// Debugln print a debug line.
+func (t discard) Debugln(v ...interface{}) {}
diff --git a/misc.go b/misc.go
index 691033849..cf89ecb25 100644
--- a/misc.go
+++ b/misc.go
@@ -90,21 +90,20 @@ func fileUploadReq(ctx context.Context, path, fieldname, filename string, values
 	return req, nil
 }
 
-func parseResponseBody(body io.ReadCloser, intf interface{}, debug bool) error {
+func parseResponseBody(body io.ReadCloser, intf interface{}, d debug) error {
 	response, err := ioutil.ReadAll(body)
 	if err != nil {
 		return err
 	}
 
-	// FIXME: will be api.Debugf
-	if debug {
-		logger.Printf("parseResponseBody: %s\n", string(response))
+	if d.Debug() {
+		d.Debugln("parseResponseBody", string(response))
 	}
 
 	return json.Unmarshal(response, intf)
 }
 
-func postLocalWithMultipartResponse(ctx context.Context, client HTTPRequester, path, fpath, fieldname string, values url.Values, intf interface{}, debug bool) error {
+func postLocalWithMultipartResponse(ctx context.Context, client httpClient, path, fpath, fieldname string, values url.Values, intf interface{}, d debug) error {
 	fullpath, err := filepath.Abs(fpath)
 	if err != nil {
 		return err
@@ -114,11 +113,11 @@ func postLocalWithMultipartResponse(ctx context.Context, client HTTPRequester, p
 		return err
 	}
 	defer file.Close()
-	return postWithMultipartResponse(ctx, client, path, filepath.Base(fpath), fieldname, values, file, intf, debug)
+	return postWithMultipartResponse(ctx, client, path, filepath.Base(fpath), fieldname, values, file, intf, d)
 }
 
-func postWithMultipartResponse(ctx context.Context, client HTTPRequester, path, name, fieldname string, values url.Values, r io.Reader, intf interface{}, debug bool) error {
-	req, err := fileUploadReq(ctx, SLACK_API+path, fieldname, name, values, r)
+func postWithMultipartResponse(ctx context.Context, client httpClient, path, name, fieldname string, values url.Values, r io.Reader, intf interface{}, d debug) error {
+	req, err := fileUploadReq(ctx, APIURL+path, fieldname, name, values, r)
 	if err != nil {
 		return err
 	}
@@ -139,14 +138,14 @@ func postWithMultipartResponse(ctx context.Context, client HTTPRequester, path,
 
 	// Slack seems to send an HTML body along with 5xx error codes. Don't parse it.
 	if resp.StatusCode != http.StatusOK {
-		logResponse(resp, debug)
+		logResponse(resp, d)
 		return statusCodeError{Code: resp.StatusCode, Status: resp.Status}
 	}
 
-	return parseResponseBody(resp.Body, intf, debug)
+	return parseResponseBody(resp.Body, intf, d)
 }
 
-func doPost(ctx context.Context, client HTTPRequester, req *http.Request, intf interface{}, debug bool) error {
+func doPost(ctx context.Context, client httpClient, req *http.Request, intf interface{}, d debug) error {
 	req = req.WithContext(ctx)
 	resp, err := client.Do(req)
 	if err != nil {
@@ -164,15 +163,15 @@ func doPost(ctx context.Context, client HTTPRequester, req *http.Request, intf i
 
 	// Slack seems to send an HTML body along with 5xx error codes. Don't parse it.
 	if resp.StatusCode != http.StatusOK {
-		logResponse(resp, debug)
+		logResponse(resp, d)
 		return statusCodeError{Code: resp.StatusCode, Status: resp.Status}
 	}
 
-	return parseResponseBody(resp.Body, intf, debug)
+	return parseResponseBody(resp.Body, intf, d)
 }
 
 // post JSON.
-func postJSON(ctx context.Context, client HTTPRequester, endpoint, token string, json []byte, intf interface{}, debug bool) error {
+func postJSON(ctx context.Context, client httpClient, endpoint, token string, json []byte, intf interface{}, d debug) error {
 	reqBody := bytes.NewBuffer(json)
 	req, err := http.NewRequest("POST", endpoint, reqBody)
 	if err != nil {
@@ -180,38 +179,37 @@ func postJSON(ctx context.Context, client HTTPRequester, endpoint, token string,
 	}
 	req.Header.Set("Content-Type", "application/json")
 	req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", token))
-	return doPost(ctx, client, req, intf, debug)
+	return doPost(ctx, client, req, intf, d)
 }
 
 // post a url encoded form.
-func postForm(ctx context.Context, client HTTPRequester, endpoint string, values url.Values, intf interface{}, debug bool) error {
+func postForm(ctx context.Context, client httpClient, endpoint string, values url.Values, intf interface{}, d debug) error {
 	reqBody := strings.NewReader(values.Encode())
 	req, err := http.NewRequest("POST", endpoint, reqBody)
 	if err != nil {
 		return err
 	}
 	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
-	return doPost(ctx, client, req, intf, debug)
+	return doPost(ctx, client, req, intf, d)
 }
 
 // post to a slack web method.
-func postSlackMethod(ctx context.Context, client HTTPRequester, path string, values url.Values, intf interface{}, debug bool) error {
-	return postForm(ctx, client, SLACK_API+path, values, intf, debug)
+func postSlackMethod(ctx context.Context, client httpClient, path string, values url.Values, intf interface{}, d debug) error {
+	return postForm(ctx, client, APIURL+path, values, intf, d)
 }
 
-func parseAdminResponse(ctx context.Context, client HTTPRequester, method string, teamName string, values url.Values, intf interface{}, debug bool) error {
-	endpoint := fmt.Sprintf(SLACK_WEB_API_FORMAT, teamName, method, time.Now().Unix())
-	return postForm(ctx, client, endpoint, values, intf, debug)
+func parseAdminResponse(ctx context.Context, client httpClient, method string, teamName string, values url.Values, intf interface{}, d debug) error {
+	endpoint := fmt.Sprintf(WEBAPIURLFormat, teamName, method, time.Now().Unix())
+	return postForm(ctx, client, endpoint, values, intf, d)
 }
 
-func logResponse(resp *http.Response, debug bool) error {
-	if debug {
+func logResponse(resp *http.Response, d debug) error {
+	if d.Debug() {
 		text, err := httputil.DumpResponse(resp, true)
 		if err != nil {
 			return err
 		}
-
-		logger.Print(string(text))
+		d.Debugln(string(text))
 	}
 
 	return nil
diff --git a/misc_test.go b/misc_test.go
index 68ddf6c8a..d0ea4d2ca 100644
--- a/misc_test.go
+++ b/misc_test.go
@@ -36,12 +36,12 @@ func setParseResponseHandler() {
 func TestParseResponse(t *testing.T) {
 	parseResponseOnce.Do(setParseResponseHandler)
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	values := url.Values{
 		"token": {validToken},
 	}
 	responsePartial := &SlackResponse{}
-	err := postSlackMethod(context.Background(), http.DefaultClient, "parseResponse", values, responsePartial, false)
+	err := postSlackMethod(context.Background(), http.DefaultClient, "parseResponse", values, responsePartial, discard{})
 	if err != nil {
 		t.Errorf("Unexpected error: %s", err)
 	}
@@ -50,10 +50,10 @@ func TestParseResponse(t *testing.T) {
 func TestParseResponseNoToken(t *testing.T) {
 	parseResponseOnce.Do(setParseResponseHandler)
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	values := url.Values{}
 	responsePartial := &SlackResponse{}
-	err := postSlackMethod(context.Background(), http.DefaultClient, "parseResponse", values, responsePartial, false)
+	err := postSlackMethod(context.Background(), http.DefaultClient, "parseResponse", values, responsePartial, discard{})
 	if err != nil {
 		t.Errorf("Unexpected error: %s", err)
 		return
@@ -68,12 +68,12 @@ func TestParseResponseNoToken(t *testing.T) {
 func TestParseResponseInvalidToken(t *testing.T) {
 	parseResponseOnce.Do(setParseResponseHandler)
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	values := url.Values{
 		"token": {"whatever"},
 	}
 	responsePartial := &SlackResponse{}
-	err := postSlackMethod(context.Background(), http.DefaultClient, "parseResponse", values, responsePartial, false)
+	err := postSlackMethod(context.Background(), http.DefaultClient, "parseResponse", values, responsePartial, discard{})
 	if err != nil {
 		t.Errorf("Unexpected error: %s", err)
 		return
diff --git a/oauth.go b/oauth.go
index 378af4a54..904012188 100644
--- a/oauth.go
+++ b/oauth.go
@@ -6,6 +6,7 @@ import (
 	"net/url"
 )
 
+// OAuthResponseIncomingWebhook ...
 type OAuthResponseIncomingWebhook struct {
 	URL              string `json:"url"`
 	Channel          string `json:"channel"`
@@ -13,11 +14,13 @@ type OAuthResponseIncomingWebhook struct {
 	ConfigurationURL string `json:"configuration_url"`
 }
 
+// OAuthResponseBot ...
 type OAuthResponseBot struct {
 	BotUserID      string `json:"bot_user_id"`
 	BotAccessToken string `json:"bot_access_token"`
 }
 
+// OAuthResponse ...
 type OAuthResponse struct {
 	AccessToken     string                       `json:"access_token"`
 	Scope           string                       `json:"scope"`
@@ -30,24 +33,24 @@ type OAuthResponse struct {
 }
 
 // GetOAuthToken retrieves an AccessToken
-func GetOAuthToken(clientID, clientSecret, code, redirectURI string, debug bool) (accessToken string, scope string, err error) {
-	return GetOAuthTokenContext(context.Background(), clientID, clientSecret, code, redirectURI, debug)
+func GetOAuthToken(client httpClient, clientID, clientSecret, code, redirectURI string, d debug) (accessToken string, scope string, err error) {
+	return GetOAuthTokenContext(context.Background(), client, clientID, clientSecret, code, redirectURI, d)
 }
 
 // GetOAuthTokenContext retrieves an AccessToken with a custom context
-func GetOAuthTokenContext(ctx context.Context, clientID, clientSecret, code, redirectURI string, debug bool) (accessToken string, scope string, err error) {
-	response, err := GetOAuthResponseContext(ctx, clientID, clientSecret, code, redirectURI, debug)
+func GetOAuthTokenContext(ctx context.Context, client httpClient, clientID, clientSecret, code, redirectURI string, d debug) (accessToken string, scope string, err error) {
+	response, err := GetOAuthResponseContext(ctx, client, clientID, clientSecret, code, redirectURI, d)
 	if err != nil {
 		return "", "", err
 	}
 	return response.AccessToken, response.Scope, nil
 }
 
-func GetOAuthResponse(clientID, clientSecret, code, redirectURI string, debug bool) (resp *OAuthResponse, err error) {
-	return GetOAuthResponseContext(context.Background(), clientID, clientSecret, code, redirectURI, debug)
+func GetOAuthResponse(client httpClient, clientID, clientSecret, code, redirectURI string, d debug) (resp *OAuthResponse, err error) {
+	return GetOAuthResponseContext(context.Background(), client, clientID, clientSecret, code, redirectURI, d)
 }
 
-func GetOAuthResponseContext(ctx context.Context, clientID, clientSecret, code, redirectURI string, debug bool) (resp *OAuthResponse, err error) {
+func GetOAuthResponseContext(ctx context.Context, client httpClient, clientID, clientSecret, code, redirectURI string, d debug) (resp *OAuthResponse, err error) {
 	values := url.Values{
 		"client_id":     {clientID},
 		"client_secret": {clientSecret},
@@ -55,7 +58,7 @@ func GetOAuthResponseContext(ctx context.Context, clientID, clientSecret, code,
 		"redirect_uri":  {redirectURI},
 	}
 	response := &OAuthResponse{}
-	err = postSlackMethod(ctx, customHTTPClient, "oauth.access", values, response, debug)
+	err = postSlackMethod(ctx, client, "oauth.access", values, response, d)
 	if err != nil {
 		return nil, err
 	}
diff --git a/pins.go b/pins.go
index 34863f17b..c1d525df2 100644
--- a/pins.go
+++ b/pins.go
@@ -34,7 +34,7 @@ func (api *Client) AddPinContext(ctx context.Context, channel string, item ItemR
 	}
 
 	response := &SlackResponse{}
-	if err := postSlackMethod(ctx, api.httpclient, "pins.add", values, response, api.debug); err != nil {
+	if err := postSlackMethod(ctx, api.httpclient, "pins.add", values, response, api); err != nil {
 		return err
 	}
 
@@ -63,7 +63,7 @@ func (api *Client) RemovePinContext(ctx context.Context, channel string, item It
 	}
 
 	response := &SlackResponse{}
-	if err := postSlackMethod(ctx, api.httpclient, "pins.remove", values, response, api.debug); err != nil {
+	if err := postSlackMethod(ctx, api.httpclient, "pins.remove", values, response, api); err != nil {
 		return err
 	}
 
@@ -83,7 +83,7 @@ func (api *Client) ListPinsContext(ctx context.Context, channel string) ([]Item,
 	}
 
 	response := &listPinsResponseFull{}
-	err := postSlackMethod(ctx, api.httpclient, "pins.list", values, response, api.debug)
+	err := postSlackMethod(ctx, api.httpclient, "pins.list", values, response, api)
 	if err != nil {
 		return nil, nil, err
 	}
diff --git a/pins_test.go b/pins_test.go
index 80f25b01b..a64eafb84 100644
--- a/pins_test.go
+++ b/pins_test.go
@@ -38,7 +38,7 @@ func (rh *pinsHandler) handler(w http.ResponseWriter, r *http.Request) {
 
 func TestSlack_AddPin(t *testing.T) {
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	tests := []struct {
 		channel    string
@@ -86,7 +86,7 @@ func TestSlack_AddPin(t *testing.T) {
 
 func TestSlack_RemovePin(t *testing.T) {
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	tests := []struct {
 		channel    string
@@ -134,7 +134,7 @@ func TestSlack_RemovePin(t *testing.T) {
 
 func TestSlack_ListPins(t *testing.T) {
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	rh := newPinsHandler()
 	http.HandleFunc("/pins.list", func(w http.ResponseWriter, r *http.Request) { rh.handler(w, r) })
diff --git a/reactions.go b/reactions.go
index 5eabde637..abe1e72ad 100644
--- a/reactions.go
+++ b/reactions.go
@@ -155,7 +155,7 @@ func (api *Client) AddReactionContext(ctx context.Context, name string, item Ite
 	}
 
 	response := &SlackResponse{}
-	if err := postSlackMethod(ctx, api.httpclient, "reactions.add", values, response, api.debug); err != nil {
+	if err := postSlackMethod(ctx, api.httpclient, "reactions.add", values, response, api); err != nil {
 		return err
 	}
 
@@ -189,7 +189,7 @@ func (api *Client) RemoveReactionContext(ctx context.Context, name string, item
 	}
 
 	response := &SlackResponse{}
-	if err := postSlackMethod(ctx, api.httpclient, "reactions.remove", values, response, api.debug); err != nil {
+	if err := postSlackMethod(ctx, api.httpclient, "reactions.remove", values, response, api); err != nil {
 		return err
 	}
 
@@ -223,7 +223,7 @@ func (api *Client) GetReactionsContext(ctx context.Context, item ItemRef, params
 	}
 
 	response := &getReactionsResponseFull{}
-	if err := postSlackMethod(ctx, api.httpclient, "reactions.get", values, response, api.debug); err != nil {
+	if err := postSlackMethod(ctx, api.httpclient, "reactions.get", values, response, api); err != nil {
 		return nil, err
 	}
 	if !response.Ok {
@@ -256,7 +256,7 @@ func (api *Client) ListReactionsContext(ctx context.Context, params ListReaction
 	}
 
 	response := &listReactionsResponseFull{}
-	err := postSlackMethod(ctx, api.httpclient, "reactions.list", values, response, api.debug)
+	err := postSlackMethod(ctx, api.httpclient, "reactions.list", values, response, api)
 	if err != nil {
 		return nil, nil, err
 	}
diff --git a/reactions_test.go b/reactions_test.go
index f032696cd..0a4a54373 100644
--- a/reactions_test.go
+++ b/reactions_test.go
@@ -41,7 +41,7 @@ func (rh *reactionsHandler) handler(w http.ResponseWriter, r *http.Request) {
 
 func TestSlack_AddReaction(t *testing.T) {
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	tests := []struct {
 		name       string
@@ -90,7 +90,7 @@ func TestSlack_AddReaction(t *testing.T) {
 
 func TestSlack_RemoveReaction(t *testing.T) {
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	tests := []struct {
 		name       string
@@ -139,7 +139,7 @@ func TestSlack_RemoveReaction(t *testing.T) {
 
 func TestSlack_GetReactions(t *testing.T) {
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	tests := []struct {
 		ref           ItemRef
@@ -254,7 +254,7 @@ func TestSlack_GetReactions(t *testing.T) {
 
 func TestSlack_ListReactions(t *testing.T) {
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	rh := newReactionsHandler()
 	http.HandleFunc("/reactions.list", func(w http.ResponseWriter, r *http.Request) { rh.handler(w, r) })
diff --git a/rtm.go b/rtm.go
index 41a136ebb..2aea30f7e 100644
--- a/rtm.go
+++ b/rtm.go
@@ -38,7 +38,7 @@ func (api *Client) StartRTM() (info *Info, websocketURL string, err error) {
 // To have a fully managed Websocket connection, use `NewRTM`, and call `ManageConnection()` on it.
 func (api *Client) StartRTMContext(ctx context.Context) (info *Info, websocketURL string, err error) {
 	response := &infoResponseFull{}
-	err = postSlackMethod(ctx, api.httpclient, "rtm.start", url.Values{"token": {api.token}}, response, api.debug)
+	err = postSlackMethod(ctx, api.httpclient, "rtm.start", url.Values{"token": {api.token}}, response, api)
 	if err != nil {
 		return nil, "", err
 	}
@@ -63,7 +63,7 @@ func (api *Client) ConnectRTM() (info *Info, websocketURL string, err error) {
 // To have a fully managed Websocket connection, use `NewRTM`, and call `ManageConnection()` on it.
 func (api *Client) ConnectRTMContext(ctx context.Context) (info *Info, websocketURL string, err error) {
 	response := &infoResponseFull{}
-	err = postSlackMethod(ctx, api.httpclient, "rtm.connect", url.Values{"token": {api.token}}, response, api.debug)
+	err = postSlackMethod(ctx, api.httpclient, "rtm.connect", url.Values{"token": {api.token}}, response, api)
 	if err != nil {
 		api.Debugf("Failed to connect to RTM: %s", err)
 		return nil, "", err
@@ -105,12 +105,12 @@ func RTMOptionPingInterval(d time.Duration) RTMOption {
 func (api *Client) NewRTM(options ...RTMOption) *RTM {
 	result := &RTM{
 		Client:           *api,
+		wasIntentional:   true,
+		isConnected:      false,
 		IncomingEvents:   make(chan RTMEvent, 50),
 		outgoingMessages: make(chan OutgoingMessage, 20),
 		pingInterval:     defaultPingInterval,
 		pingDeadman:      time.NewTimer(deadmanDuration(defaultPingInterval)),
-		isConnected:      false,
-		wasIntentional:   true,
 		killChannel:      make(chan bool),
 		disconnected:     make(chan struct{}, 1),
 		forcePing:        make(chan bool),
@@ -125,14 +125,3 @@ func (api *Client) NewRTM(options ...RTMOption) *RTM {
 
 	return result
 }
-
-// NewRTMWithOptions Deprecated just use NewRTM(RTMOptionsUseStart(true))
-// returns a RTM, which provides a fully managed connection to
-// Slack's websocket-based Real-Time Messaging protocol.
-// This also allows to configure various options available for RTM API.
-func (api *Client) NewRTMWithOptions(options *RTMOptions) *RTM {
-	if options != nil {
-		return api.NewRTM(RTMOptionUseStart(options.UseRTMStart))
-	}
-	return api.NewRTM()
-}
diff --git a/search.go b/search.go
index e858952f4..2d018fcc6 100644
--- a/search.go
+++ b/search.go
@@ -2,7 +2,6 @@ package slack
 
 import (
 	"context"
-	"errors"
 	"net/url"
 	"strconv"
 )
@@ -104,14 +103,12 @@ func (api *Client) _search(ctx context.Context, path, query string, params Searc
 	}
 
 	response = &searchResponseFull{}
-	err := postSlackMethod(ctx, api.httpclient, path, values, response, api.debug)
+	err := postSlackMethod(ctx, api.httpclient, path, values, response, api)
 	if err != nil {
 		return nil, err
 	}
-	if !response.Ok {
-		return nil, errors.New(response.Error)
-	}
-	return response, nil
+
+	return response, response.Err()
 
 }
 
diff --git a/slack.go b/slack.go
index 6d1e7de9c..f80bf1572 100644
--- a/slack.go
+++ b/slack.go
@@ -2,7 +2,6 @@ package slack
 
 import (
 	"context"
-	"errors"
 	"fmt"
 	"log"
 	"net/http"
@@ -10,31 +9,17 @@ import (
 	"os"
 )
 
-// Added as a var so that we can change this for testing purposes
-var SLACK_API string = "https://slack.com/api/"
-var SLACK_WEB_API_FORMAT string = "https://%s.slack.com/api/users.admin.%s?t=%s"
+// APIURL a dded as a var so that we can change this for testing purposes
+var APIURL = "https://slack.com/api/"
 
-// HTTPClient sets a custom http.Client
-// deprecated: in favor of SetHTTPClient()
-var HTTPClient = &http.Client{}
+// WEBAPIURLFormat ...
+var WEBAPIURLFormat = "https://%s.slack.com/api/users.admin.%s?t=%s"
 
-var customHTTPClient HTTPRequester = HTTPClient
-
-// HTTPRequester defines the minimal interface needed for an http.Client to be implemented.
-//
-// Use it in conjunction with the SetHTTPClient function to allow for other capabilities
-// like a tracing http.Client
-type HTTPRequester interface {
+// httpClient defines the minimal interface needed for an http.Client to be implemented.
+type httpClient interface {
 	Do(*http.Request) (*http.Response, error)
 }
 
-// SetHTTPClient allows you to specify a custom http.Client
-// Use this instead of the package level HTTPClient variable if you want to use a custom client like the
-// Stackdriver Trace HTTPClient https://godoc.org/cloud.google.com/go/trace#HTTPClient
-func SetHTTPClient(client HTTPRequester) {
-	customHTTPClient = client
-}
-
 // ResponseMetadata holds pagination metadata
 type ResponseMetadata struct {
 	Cursor string `json:"next_cursor"`
@@ -48,6 +33,7 @@ func (t *ResponseMetadata) initialize() *ResponseMetadata {
 	return &ResponseMetadata{}
 }
 
+// AuthTestResponse ...
 type AuthTestResponse struct {
 	URL    string `json:"url"`
 	Team   string `json:"team"`
@@ -61,20 +47,36 @@ type authTestResponseFull struct {
 	AuthTestResponse
 }
 
+// Client for the slack api.
 type Client struct {
 	token      string
 	info       Info
 	debug      bool
-	httpclient HTTPRequester
+	log        logInternal
+	httpclient httpClient
 }
 
 // Option defines an option for a Client
 type Option func(*Client)
 
 // OptionHTTPClient - provide a custom http client to the slack client.
-func OptionHTTPClient(c HTTPRequester) func(*Client) {
-	return func(s *Client) {
-		s.httpclient = c
+func OptionHTTPClient(client httpClient) func(*Client) {
+	return func(c *Client) {
+		c.httpclient = client
+	}
+}
+
+// OptionDebug enable debugging for the client
+func OptionDebug(b bool) func(*Client) {
+	return func(c *Client) {
+		c.debug = b
+	}
+}
+
+// OptionLog set logging for client.
+func OptionLog(l logProvider) func(*Client) {
+	return func(c *Client) {
+		c.log = ilogger{logProvider: l}
 	}
 }
 
@@ -82,7 +84,8 @@ func OptionHTTPClient(c HTTPRequester) func(*Client) {
 func New(token string, options ...Option) *Client {
 	s := &Client{
 		token:      token,
-		httpclient: customHTTPClient,
+		httpclient: &http.Client{},
+		log:        log.New(os.Stdout, "nlopes/slack", log.LstdFlags|log.Lshortfile),
 	}
 
 	for _, opt := range options {
@@ -98,43 +101,32 @@ func (api *Client) AuthTest() (response *AuthTestResponse, error error) {
 }
 
 // AuthTestContext tests if the user is able to do authenticated requests or not with a custom context
-func (api *Client) AuthTestContext(ctx context.Context) (response *AuthTestResponse, error error) {
+func (api *Client) AuthTestContext(ctx context.Context) (response *AuthTestResponse, err error) {
 	api.Debugf("Challenging auth...")
 	responseFull := &authTestResponseFull{}
-	err := postSlackMethod(ctx, api.httpclient, "auth.test", url.Values{"token": {api.token}}, responseFull, api.debug)
+	err = postSlackMethod(ctx, api.httpclient, "auth.test", url.Values{"token": {api.token}}, responseFull, api)
 	if err != nil {
-		api.Debugf("failed to test for auth: %s", err)
 		return nil, err
 	}
-	if !responseFull.Ok {
-		api.Debugf("auth response was not Ok: %s", responseFull.Error)
-		return nil, errors.New(responseFull.Error)
-	}
 
-	api.Debugf("Auth challenge was successful with response %+v", responseFull.AuthTestResponse)
-	return &responseFull.AuthTestResponse, nil
-}
-
-// SetDebug switches the api into debug mode
-// When in debug mode, it logs various info about what its doing
-// If you ever use this in production, don't call SetDebug(true)
-func (api *Client) SetDebug(debug bool) {
-	api.debug = debug
-	if debug && logger == nil {
-		SetLogger(log.New(os.Stdout, "nlopes/slack", log.LstdFlags|log.Lshortfile))
-	}
+	return &responseFull.AuthTestResponse, responseFull.Err()
 }
 
 // Debugf print a formatted debug line.
 func (api *Client) Debugf(format string, v ...interface{}) {
 	if api.debug {
-		logger.Output(2, fmt.Sprintf(format, v...))
+		api.log.Output(2, fmt.Sprintf(format, v...))
 	}
 }
 
 // Debugln print a debug line.
 func (api *Client) Debugln(v ...interface{}) {
 	if api.debug {
-		logger.Output(2, fmt.Sprintln(v...))
+		api.log.Output(2, fmt.Sprintln(v...))
 	}
 }
+
+// Debug returns if debug is enabled.
+func (api *Client) Debug() bool {
+	return api.debug
+}
diff --git a/stars.go b/stars.go
index c1e2f6cb7..7e1e621d1 100644
--- a/stars.go
+++ b/stars.go
@@ -58,7 +58,7 @@ func (api *Client) AddStarContext(ctx context.Context, channel string, item Item
 	}
 
 	response := &SlackResponse{}
-	if err := postSlackMethod(ctx, api.httpclient, "stars.add", values, response, api.debug); err != nil {
+	if err := postSlackMethod(ctx, api.httpclient, "stars.add", values, response, api); err != nil {
 		return err
 	}
 
@@ -87,7 +87,7 @@ func (api *Client) RemoveStarContext(ctx context.Context, channel string, item I
 	}
 
 	response := &SlackResponse{}
-	if err := postSlackMethod(ctx, api.httpclient, "stars.remove", values, response, api.debug); err != nil {
+	if err := postSlackMethod(ctx, api.httpclient, "stars.remove", values, response, api); err != nil {
 		return err
 	}
 
@@ -115,7 +115,7 @@ func (api *Client) ListStarsContext(ctx context.Context, params StarsParameters)
 	}
 
 	response := &listResponseFull{}
-	err := postSlackMethod(ctx, api.httpclient, "stars.list", values, response, api.debug)
+	err := postSlackMethod(ctx, api.httpclient, "stars.list", values, response, api)
 	if err != nil {
 		return nil, nil, err
 	}
diff --git a/stars_test.go b/stars_test.go
index 65696b9ae..a4803850d 100644
--- a/stars_test.go
+++ b/stars_test.go
@@ -39,7 +39,7 @@ func (sh *starsHandler) handler(w http.ResponseWriter, r *http.Request) {
 
 func TestSlack_AddStar(t *testing.T) {
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	tests := []struct {
 		channel    string
@@ -87,7 +87,7 @@ func TestSlack_AddStar(t *testing.T) {
 
 func TestSlack_RemoveStar(t *testing.T) {
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	tests := []struct {
 		channel    string
@@ -135,7 +135,7 @@ func TestSlack_RemoveStar(t *testing.T) {
 
 func TestSlack_ListStars(t *testing.T) {
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	rh := newStarsHandler()
 	http.HandleFunc("/stars.list", func(w http.ResponseWriter, r *http.Request) { rh.handler(w, r) })
diff --git a/team.go b/team.go
index b6e341ebf..1892cf5f8 100644
--- a/team.go
+++ b/team.go
@@ -2,7 +2,6 @@ package slack
 
 import (
 	"context"
-	"errors"
 	"net/url"
 	"strconv"
 )
@@ -67,44 +66,33 @@ func NewAccessLogParameters() AccessLogParameters {
 	}
 }
 
-func teamRequest(ctx context.Context, client HTTPRequester, path string, values url.Values, debug bool) (*TeamResponse, error) {
+func teamRequest(ctx context.Context, client httpClient, path string, values url.Values, d debug) (*TeamResponse, error) {
 	response := &TeamResponse{}
-	err := postSlackMethod(ctx, client, path, values, response, debug)
+	err := postSlackMethod(ctx, client, path, values, response, d)
 	if err != nil {
 		return nil, err
 	}
 
-	if !response.Ok {
-		return nil, errors.New(response.Error)
-	}
-
-	return response, nil
+	return response, response.Err()
 }
 
-func billableInfoRequest(ctx context.Context, client HTTPRequester, path string, values url.Values, debug bool) (map[string]BillingActive, error) {
+func billableInfoRequest(ctx context.Context, client httpClient, path string, values url.Values, d debug) (map[string]BillingActive, error) {
 	response := &BillableInfoResponse{}
-	err := postSlackMethod(ctx, client, path, values, response, debug)
+	err := postSlackMethod(ctx, client, path, values, response, d)
 	if err != nil {
 		return nil, err
 	}
 
-	if !response.Ok {
-		return nil, errors.New(response.Error)
-	}
-
-	return response.BillableInfo, nil
+	return response.BillableInfo, response.Err()
 }
 
-func accessLogsRequest(ctx context.Context, client HTTPRequester, path string, values url.Values, debug bool) (*LoginResponse, error) {
+func accessLogsRequest(ctx context.Context, client httpClient, path string, values url.Values, d debug) (*LoginResponse, error) {
 	response := &LoginResponse{}
-	err := postSlackMethod(ctx, client, path, values, response, debug)
+	err := postSlackMethod(ctx, client, path, values, response, d)
 	if err != nil {
 		return nil, err
 	}
-	if !response.Ok {
-		return nil, errors.New(response.Error)
-	}
-	return response, nil
+	return response, response.Err()
 }
 
 // GetTeamInfo gets the Team Information of the user
@@ -118,7 +106,7 @@ func (api *Client) GetTeamInfoContext(ctx context.Context) (*TeamInfo, error) {
 		"token": {api.token},
 	}
 
-	response, err := teamRequest(ctx, api.httpclient, "team.info", values, api.debug)
+	response, err := teamRequest(ctx, api.httpclient, "team.info", values, api)
 	if err != nil {
 		return nil, err
 	}
@@ -142,7 +130,7 @@ func (api *Client) GetAccessLogsContext(ctx context.Context, params AccessLogPar
 		values.Add("page", strconv.Itoa(params.Page))
 	}
 
-	response, err := accessLogsRequest(ctx, api.httpclient, "team.accessLogs", values, api.debug)
+	response, err := accessLogsRequest(ctx, api.httpclient, "team.accessLogs", values, api)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -159,7 +147,7 @@ func (api *Client) GetBillableInfoContext(ctx context.Context, user string) (map
 		"user":  {user},
 	}
 
-	return billableInfoRequest(ctx, api.httpclient, "team.billableInfo", values, api.debug)
+	return billableInfoRequest(ctx, api.httpclient, "team.billableInfo", values, api)
 }
 
 // GetBillableInfoForTeam returns the billing_active status of all users on the team.
@@ -173,5 +161,5 @@ func (api *Client) GetBillableInfoForTeamContext(ctx context.Context) (map[strin
 		"token": {api.token},
 	}
 
-	return billableInfoRequest(ctx, api.httpclient, "team.billableInfo", values, api.debug)
+	return billableInfoRequest(ctx, api.httpclient, "team.billableInfo", values, api)
 }
diff --git a/team_test.go b/team_test.go
index 94ea10bc9..3497c383c 100644
--- a/team_test.go
+++ b/team_test.go
@@ -31,7 +31,7 @@ func TestGetTeamInfo(t *testing.T) {
 	http.HandleFunc("/team.info", getTeamInfo)
 
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 
 	teamInfo, err := api.GetTeamInfo()
@@ -95,7 +95,7 @@ func TestGetAccessLogs(t *testing.T) {
 	http.HandleFunc("/team.accessLogs", getTeamAccessLogs)
 
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 
 	logins, paging, err := api.GetAccessLogs(NewAccessLogParameters())
diff --git a/usergroups.go b/usergroups.go
index cc9bc4ca7..9e1452725 100644
--- a/usergroups.go
+++ b/usergroups.go
@@ -2,7 +2,6 @@ package slack
 
 import (
 	"context"
-	"errors"
 	"net/url"
 	"strings"
 )
@@ -41,16 +40,14 @@ type userGroupResponseFull struct {
 	SlackResponse
 }
 
-func userGroupRequest(ctx context.Context, client HTTPRequester, path string, values url.Values, debug bool) (*userGroupResponseFull, error) {
+func userGroupRequest(ctx context.Context, client httpClient, path string, values url.Values, d debug) (*userGroupResponseFull, error) {
 	response := &userGroupResponseFull{}
-	err := postSlackMethod(ctx, client, path, values, response, debug)
+	err := postSlackMethod(ctx, client, path, values, response, d)
 	if err != nil {
 		return nil, err
 	}
-	if !response.Ok {
-		return nil, errors.New(response.Error)
-	}
-	return response, nil
+
+	return response, response.Err()
 }
 
 // CreateUserGroup creates a new user group
@@ -77,7 +74,7 @@ func (api *Client) CreateUserGroupContext(ctx context.Context, userGroup UserGro
 		values["channels"] = []string{strings.Join(userGroup.Prefs.Channels, ",")}
 	}
 
-	response, err := userGroupRequest(ctx, api.httpclient, "usergroups.create", values, api.debug)
+	response, err := userGroupRequest(ctx, api.httpclient, "usergroups.create", values, api)
 	if err != nil {
 		return UserGroup{}, err
 	}
@@ -96,7 +93,7 @@ func (api *Client) DisableUserGroupContext(ctx context.Context, userGroup string
 		"usergroup": {userGroup},
 	}
 
-	response, err := userGroupRequest(ctx, api.httpclient, "usergroups.disable", values, api.debug)
+	response, err := userGroupRequest(ctx, api.httpclient, "usergroups.disable", values, api)
 	if err != nil {
 		return UserGroup{}, err
 	}
@@ -115,7 +112,7 @@ func (api *Client) EnableUserGroupContext(ctx context.Context, userGroup string)
 		"usergroup": {userGroup},
 	}
 
-	response, err := userGroupRequest(ctx, api.httpclient, "usergroups.enable", values, api.debug)
+	response, err := userGroupRequest(ctx, api.httpclient, "usergroups.enable", values, api)
 	if err != nil {
 		return UserGroup{}, err
 	}
@@ -179,7 +176,7 @@ func (api *Client) GetUserGroupsContext(ctx context.Context, options ...GetUserG
 		values.Add("include_users", "true")
 	}
 
-	response, err := userGroupRequest(ctx, api.httpclient, "usergroups.list", values, api.debug)
+	response, err := userGroupRequest(ctx, api.httpclient, "usergroups.list", values, api)
 	if err != nil {
 		return nil, err
 	}
@@ -210,7 +207,7 @@ func (api *Client) UpdateUserGroupContext(ctx context.Context, userGroup UserGro
 		values["description"] = []string{userGroup.Description}
 	}
 
-	response, err := userGroupRequest(ctx, api.httpclient, "usergroups.update", values, api.debug)
+	response, err := userGroupRequest(ctx, api.httpclient, "usergroups.update", values, api)
 	if err != nil {
 		return UserGroup{}, err
 	}
@@ -229,7 +226,7 @@ func (api *Client) GetUserGroupMembersContext(ctx context.Context, userGroup str
 		"usergroup": {userGroup},
 	}
 
-	response, err := userGroupRequest(ctx, api.httpclient, "usergroups.users.list", values, api.debug)
+	response, err := userGroupRequest(ctx, api.httpclient, "usergroups.users.list", values, api)
 	if err != nil {
 		return []string{}, err
 	}
@@ -249,7 +246,7 @@ func (api *Client) UpdateUserGroupMembersContext(ctx context.Context, userGroup
 		"users":     {members},
 	}
 
-	response, err := userGroupRequest(ctx, api.httpclient, "usergroups.users.update", values, api.debug)
+	response, err := userGroupRequest(ctx, api.httpclient, "usergroups.users.update", values, api)
 	if err != nil {
 		return UserGroup{}, err
 	}
diff --git a/usergroups_test.go b/usergroups_test.go
index ba3b97f18..7f3ab6bf8 100644
--- a/usergroups_test.go
+++ b/usergroups_test.go
@@ -61,7 +61,7 @@ func (ugh *userGroupsHandler) handler(w http.ResponseWriter, r *http.Request) {
 
 func TestCreateUserGroup(t *testing.T) {
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 
 	tests := []struct {
@@ -142,7 +142,7 @@ func TestGetUserGroups(t *testing.T) {
 	http.HandleFunc("/usergroups.list", getUserGroups)
 
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 
 	userGroups, err := api.GetUserGroups(GetUserGroupsOptionIncludeUsers(true))
diff --git a/users.go b/users.go
index 0dd20db57..aa941a740 100644
--- a/users.go
+++ b/users.go
@@ -189,16 +189,14 @@ func NewUserSetPhotoParams() UserSetPhotoParams {
 	}
 }
 
-func userRequest(ctx context.Context, client HTTPRequester, path string, values url.Values, debug bool) (*userResponseFull, error) {
+func userRequest(ctx context.Context, client httpClient, path string, values url.Values, d debug) (*userResponseFull, error) {
 	response := &userResponseFull{}
-	err := postForm(ctx, client, SLACK_API+path, values, response, debug)
+	err := postForm(ctx, client, APIURL+path, values, response, d)
 	if err != nil {
 		return nil, err
 	}
-	if !response.Ok {
-		return nil, errors.New(response.Error)
-	}
-	return response, nil
+
+	return response, response.Err()
 }
 
 // GetUserPresence will retrieve the current presence status of given user.
@@ -213,7 +211,7 @@ func (api *Client) GetUserPresenceContext(ctx context.Context, user string) (*Us
 		"user":  {user},
 	}
 
-	response, err := userRequest(ctx, api.httpclient, "users.getPresence", values, api.debug)
+	response, err := userRequest(ctx, api.httpclient, "users.getPresence", values, api)
 	if err != nil {
 		return nil, err
 	}
@@ -232,7 +230,7 @@ func (api *Client) GetUserInfoContext(ctx context.Context, user string) (*User,
 		"user":  {user},
 	}
 
-	response, err := userRequest(ctx, api.httpclient, "users.info", values, api.debug)
+	response, err := userRequest(ctx, api.httpclient, "users.info", values, api)
 	if err != nil {
 		return nil, err
 	}
@@ -310,7 +308,7 @@ func (t UserPagination) Next(ctx context.Context) (_ UserPagination, err error)
 		"cursor":   {t.previousResp.Cursor},
 	}
 
-	if resp, err = userRequest(ctx, t.c.httpclient, "users.list", values, t.c.debug); err != nil {
+	if resp, err = userRequest(ctx, t.c.httpclient, "users.list", values, t.c); err != nil {
 		return t, err
 	}
 
@@ -355,7 +353,7 @@ func (api *Client) GetUserByEmailContext(ctx context.Context, email string) (*Us
 		"token": {api.token},
 		"email": {email},
 	}
-	response, err := userRequest(ctx, api.httpclient, "users.lookupByEmail", values, api.debug)
+	response, err := userRequest(ctx, api.httpclient, "users.lookupByEmail", values, api)
 	if err != nil {
 		return nil, err
 	}
@@ -373,7 +371,7 @@ func (api *Client) SetUserAsActiveContext(ctx context.Context) (err error) {
 		"token": {api.token},
 	}
 
-	_, err = userRequest(ctx, api.httpclient, "users.setActive", values, api.debug)
+	_, err = userRequest(ctx, api.httpclient, "users.setActive", values, api)
 	return err
 }
 
@@ -389,7 +387,7 @@ func (api *Client) SetUserPresenceContext(ctx context.Context, presence string)
 		"presence": {presence},
 	}
 
-	_, err := userRequest(ctx, api.httpclient, "users.setPresence", values, api.debug)
+	_, err := userRequest(ctx, api.httpclient, "users.setPresence", values, api)
 	return err
 }
 
@@ -405,7 +403,7 @@ func (api *Client) GetUserIdentityContext(ctx context.Context) (*UserIdentityRes
 	}
 	response := &UserIdentityResponse{}
 
-	err := postForm(ctx, api.httpclient, SLACK_API+"users.identity", values, response, api.debug)
+	err := postForm(ctx, api.httpclient, APIURL+"users.identity", values, response, api)
 	if err != nil {
 		return nil, err
 	}
@@ -436,7 +434,7 @@ func (api *Client) SetUserPhotoContext(ctx context.Context, image string, params
 		values.Add("crop_w", strconv.Itoa(params.CropW))
 	}
 
-	err := postLocalWithMultipartResponse(ctx, api.httpclient, "users.setPhoto", image, "image", values, response, api.debug)
+	err := postLocalWithMultipartResponse(ctx, api.httpclient, "users.setPhoto", image, "image", values, response, api)
 	if err != nil {
 		return err
 	}
@@ -456,7 +454,7 @@ func (api *Client) DeleteUserPhotoContext(ctx context.Context) error {
 		"token": {api.token},
 	}
 
-	err := postForm(ctx, api.httpclient, SLACK_API+"users.deletePhoto", values, response, api.debug)
+	err := postForm(ctx, api.httpclient, APIURL+"users.deletePhoto", values, response, api)
 	if err != nil {
 		return err
 	}
@@ -506,7 +504,7 @@ func (api *Client) SetUserCustomStatusContext(ctx context.Context, statusText, s
 	}
 
 	response := &userResponseFull{}
-	if err = postForm(ctx, api.httpclient, SLACK_API+"users.profile.set", values, response, api.debug); err != nil {
+	if err = postForm(ctx, api.httpclient, APIURL+"users.profile.set", values, response, api); err != nil {
 		return err
 	}
 
@@ -547,7 +545,7 @@ func (api *Client) GetUserProfileContext(ctx context.Context, userID string, inc
 	}
 	resp := &getUserProfileResponse{}
 
-	err := postSlackMethod(ctx, api.httpclient, "users.profile.get", values, &resp, api.debug)
+	err := postSlackMethod(ctx, api.httpclient, "users.profile.get", values, &resp, api)
 	if err != nil {
 		return nil, err
 	}
diff --git a/users_test.go b/users_test.go
index 50dbdc679..701614061 100644
--- a/users_test.go
+++ b/users_test.go
@@ -170,7 +170,7 @@ func TestGetUserIdentity(t *testing.T) {
 	http.HandleFunc("/users.identity", getUserIdentity)
 
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 
 	identity, err := api.GetUserIdentity()
@@ -211,7 +211,7 @@ func TestGetUserByEmail(t *testing.T) {
 	expectedUser := getTestUser()
 
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 
 	user, err := api.GetUserByEmail("test@test.com")
@@ -232,7 +232,7 @@ func TestUserCustomStatus(t *testing.T) {
 	http.HandleFunc("/users.profile.set", setUserProfile)
 
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 
 	testSetUserCustomStatus(api, up, t)
@@ -277,7 +277,7 @@ func TestGetUsers(t *testing.T) {
 	expectedUser := getTestUser()
 
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 
 	users, err := api.GetUsers()
@@ -329,7 +329,7 @@ func TestSetUserPhoto(t *testing.T) {
 	http.HandleFunc("/users.setPhoto", setUserPhotoHandler(fileContent, params))
 
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New(validToken)
 
 	err := api.SetUserPhoto(file.Name(), params)
@@ -436,7 +436,7 @@ func getUserProfileHandler(rw http.ResponseWriter, r *http.Request) {
 func TestGetUserProfile(t *testing.T) {
 	http.HandleFunc("/users.profile.get", getUserProfileHandler)
 	once.Do(startServer)
-	SLACK_API = "http://" + serverAddr + "/"
+	APIURL = "http://" + serverAddr + "/"
 	api := New("testing-token")
 	profile, err := api.GetUserProfile("UXXXXXXXX", false)
 	if err != nil {
diff --git a/websocket.go b/websocket.go
index 242acf40e..b5c2b09fa 100644
--- a/websocket.go
+++ b/websocket.go
@@ -20,6 +20,9 @@ const (
 //
 // Create this element with Client's NewRTM() or NewRTMWithOptions(*RTMOptions)
 type RTM struct {
+	// Client is the main API, embedded
+	Client
+
 	idGen        IDGenerator
 	pingInterval time.Duration
 	pingDeadman  *time.Timer
@@ -35,8 +38,6 @@ type RTM struct {
 	wasIntentional   bool
 	isConnected      bool
 
-	// Client is the main API, embedded
-	Client
 	websocketURL string
 
 	// UserDetails upon connection
@@ -55,18 +56,6 @@ type RTM struct {
 	mu *sync.Mutex
 }
 
-// RTMOptions allows configuration of various options available for RTM messaging
-//
-// This structure will evolve in time so please make sure you are always using the
-// named keys for every entry available as per Go 1 compatibility promise adding fields
-// to this structure should not be considered a breaking change.
-type RTMOptions struct {
-	// UseRTMStart set to true in order to use rtm.start or false to use rtm.connect
-	// As of 11th July 2017 you should prefer setting this to false, see:
-	// https://api.slack.com/changelog/2017-04-start-using-rtm-connect-and-stop-using-rtm-start
-	UseRTMStart bool
-}
-
 // Disconnect and wait, blocking until a successful disconnection.
 func (rtm *RTM) Disconnect() error {
 	// avoid RTM disconnect race conditions
diff --git a/websocket_managed_conn.go b/websocket_managed_conn.go
index e8ab65a1e..9e71956b3 100644
--- a/websocket_managed_conn.go
+++ b/websocket_managed_conn.go
@@ -405,8 +405,7 @@ func (rtm *RTM) handlePong(event json.RawMessage) {
 	rtm.resetDeadman()
 
 	if err := json.Unmarshal(event, &p); err != nil {
-		logger.Println("RTM Error unmarshalling 'pong' event:", err)
-		rtm.Debugln(" -> Erroneous 'ping' event:", string(event))
+		rtm.Client.log.Println("RTM Error unmarshalling 'pong' event:", err)
 		return
 	}
 
@@ -423,8 +422,8 @@ func (rtm *RTM) handlePong(event json.RawMessage) {
 func (rtm *RTM) handleEvent(typeStr string, event json.RawMessage) {
 	v, exists := EventMapping[typeStr]
 	if !exists {
-		rtm.Debugf("RTM Error, received unmapped event %q: %s\n", typeStr, string(event))
-		err := fmt.Errorf("RTM Error: Received unmapped event %q: %s\n", typeStr, string(event))
+		rtm.Debugf("RTM Error - received unmapped event %q: %s\n", typeStr, string(event))
+		err := fmt.Errorf("RTM Error: Received unmapped event %q: %s", typeStr, string(event))
 		rtm.IncomingEvents <- RTMEvent{"unmarshalling_error", &UnmarshallingErrorEvent{err}}
 		return
 	}
@@ -433,7 +432,7 @@ func (rtm *RTM) handleEvent(typeStr string, event json.RawMessage) {
 	err := json.Unmarshal(event, recvEvent)
 	if err != nil {
 		rtm.Debugf("RTM Error, could not unmarshall event %q: %s\n", typeStr, string(event))
-		err := fmt.Errorf("RTM Error: Could not unmarshall event %q: %s\n", typeStr, string(event))
+		err := fmt.Errorf("RTM Error: Could not unmarshall event %q: %s", typeStr, string(event))
 		rtm.IncomingEvents <- RTMEvent{"unmarshalling_error", &UnmarshallingErrorEvent{err}}
 		return
 	}
diff --git a/websocket_managed_conn_test.go b/websocket_managed_conn_test.go
index 83e40dade..31fbedd45 100644
--- a/websocket_managed_conn_test.go
+++ b/websocket_managed_conn_test.go
@@ -19,7 +19,7 @@ func TestRTMSingleConnect(t *testing.T) {
 	go testServer.Start()
 
 	// Setup and start the RTM.
-	slack.SLACK_API = testServer.GetAPIURL()
+	slack.APIURL = testServer.GetAPIURL()
 	api := slack.New(testToken)
 	rtm := api.NewRTM(slack.RTMOptionUseStart(true))
 	go rtm.ManageConnection()