Added unit test for includeInSample

src/github.com/getlantern/flashlight/logging/logging.go

@@ -414,14 +414,13 @@ func includeInSample(deviceID string, samplePercentage float64) bool {
 		log.Debugf("Error decoding base64 deviceID %v: %v", deviceID, base64Err)
 		return false
 	}
-	var deviceIDInt uint64
 	if len(deviceIDBytes) != 6 {
 		log.Debugf("Unexpected DeviceID length %v: %d", deviceID, len(deviceIDBytes))
 		return false
 	}
 	// Pad and decode to int
 	paddedDeviceIDBytes := append(deviceIDBytes, 0, 0)
-	// Use BigEndian because Mac address has most significant bytes on left
-	deviceIDInt = binary.BigEndian.Uint64(paddedDeviceIDBytes)
+	// Use LittleEndian because Mac address has most significant bytes on left
+	deviceIDInt := binary.LittleEndian.Uint64(paddedDeviceIDBytes)
 	return deviceIDInt%uint64(1/samplePercentage) == 0
 }

src/github.com/getlantern/flashlight/logging/logging_test.go

@@ -2,6 +2,8 @@ package logging
 
 import (
 	"bytes"
+	"encoding/base64"
+	"encoding/binary"
 	"encoding/json"
 	"fmt"
 	"regexp"
@@ -112,3 +114,15 @@ func TestLoggly(t *testing.T) {
 		assert.Equal(t, 100, len(result["message"].(string)))
 	}
 }
+
+func TestIncludeInSample(t *testing.T) {
+	included := 0
+	b := make([]byte, 8)
+	for i := uint64(0); i < 100; i++ {
+		binary.LittleEndian.PutUint64(b, i)
+		if includeInSample(base64.StdEncoding.EncodeToString(b[:6]), 0.01) {
+			included++
+		}
+	}
+	assert.Equal(t, 1, included, "Only 1% should have been included")
+}