Athens: add log tests to cloud formatters (gomods#289)

* Athens: add log tests to cloud formatters

* log: consistent variable mutation in tests

* log: add testify instead of standard library

pkg/log/log_test.go

@@ -0,0 +1,92 @@
+package log
+
+import (
+	"bytes"
+	"fmt"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/sirupsen/logrus"
+)
+
+type input struct {
+	name          string
+	cloudProvider string
+	level         string
+	fields        logrus.Fields
+	logFunc       func(e Entry)
+	output        string
+}
+
+var testCases = []input{
+	{
+		name:          "gcp_debug",
+		cloudProvider: "GCP",
+		level:         "debug",
+		fields:        logrus.Fields{},
+		logFunc:       func(e Entry) { e.Infof("info message") },
+		output:        `{"message":"info message","severity":"info","timestamp":"%v"}` + "\n",
+	},
+	{
+		name:          "gcp_error",
+		cloudProvider: "GCP",
+		level:         "debug",
+		fields:        logrus.Fields{},
+		logFunc:       func(e Entry) { e.Errorf("err message") },
+		output:        `{"message":"err message","severity":"error","timestamp":"%v"}` + "\n",
+	},
+	{
+		name:          "gcp_empty",
+		cloudProvider: "GCP",
+		level:         "error",
+		fields:        logrus.Fields{},
+		logFunc:       func(e Entry) { e.Infof("info message") },
+		output:        ``,
+	},
+	{
+		name:          "gcp_fields",
+		cloudProvider: "GCP",
+		level:         "debug",
+		fields:        logrus.Fields{"field1": "value1", "field2": 2},
+		logFunc:       func(e Entry) { e.Debugf("debug message") },
+		output:        `{"field1":"value1","field2":2,"message":"debug message","severity":"debug","timestamp":"%v"}` + "\n",
+	},
+	{
+		name:          "gcp_logs",
+		cloudProvider: "GCP",
+		level:         "debug",
+		fields:        logrus.Fields{},
+		logFunc:       func(e Entry) { e.Warnf("warn message") },
+		output:        `{"message":"warn message","severity":"warning","timestamp":"%v"}` + "\n",
+	},
+	{
+		name:          "default",
+		cloudProvider: "default",
+		level:         "debug",
+		fields:        logrus.Fields{"xyz": "abc", "abc": "xyz"},
+		logFunc:       func(e Entry) { e.Warnf("warn message") },
+		output:        `{"abc":"xyz","level":"warning","msg":"warn message","time":"%v","xyz":"abc"}` + "\n",
+	},
+}
+
+func TestCloudLogger(t *testing.T) {
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			lggr := New(tc.cloudProvider, tc.level)
+			var buf bytes.Buffer
+			lggr.Out = &buf
+			e := lggr.WithFields(tc.fields)
+			tc.logFunc(e)
+			out := buf.String()
+			expected := tc.output
+			if strings.Contains(expected, "%v") {
+				expected = fmt.Sprintf(expected, time.Now().Format(time.RFC3339))
+			}
+
+			require.Equal(t, expected, out, "expected the logged entry to match the testCase output")
+		})
+	}
+}