add unit test

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

@@ -176,7 +176,7 @@ func (w logglyErrorWriter) Write(b []byte) (int, error) {
 	}
 	fullMessage := string(b)
 	message := fullMessage
-	// Loggly can't index fields with more than 100 characters
+	// Loggly doesn't group fields with more than 100 characters
 	if len(fullMessage) > 100 {
 		message = fullMessage[0:100]
 	}

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

@@ -0,0 +1,36 @@
+package logging
+
+import (
+	"bytes"
+	"encoding/json"
+	"strings"
+	"testing"
+
+	"github.com/getlantern/go-loggly"
+	"github.com/getlantern/golog"
+	"github.com/getlantern/testify/assert"
+)
+
+func TestLoggly(t *testing.T) {
+	var buf bytes.Buffer
+	var result map[string]interface{}
+	loggly := loggly.New("token not required")
+	loggly.Writer = &buf
+	lw := logglyErrorWriter{client: loggly}
+	golog.SetOutputs(lw, nil)
+	log := golog.LoggerFor("test")
+
+	log.Error("short message")
+	if assert.NoError(t, json.Unmarshal(buf.Bytes(), &result), "Unmarshal error") {
+		assert.Equal(t, "test", result["locationInfo"])
+		assert.Equal(t, "test: short message\n", result["message"])
+	}
+
+	buf.Reset()
+	longMsg := "really l" + strings.Repeat("o", 100) + "ng message"
+	log.Error(longMsg)
+	if assert.NoError(t, json.Unmarshal(buf.Bytes(), &result), "Unmarshal error") {
+		assert.Equal(t, "test", result["locationInfo"])
+		assert.Equal(t, ("test: " + longMsg)[0:100], result["message"], "message should be truncated to 100 characters")
+	}
+}