[GH-432] Add unit tests for ./services/telemetry/telemetry.go (#1091)

* Add unit tests  for ./services/telemetry/telemetry.go

* make ci happy

* Update server/services/telemetry/telemetry_test.go

Update imports

* Update server/services/telemetry/telemetry_test.go

* Update server/services/telemetry/telemetry_test.go

* Update server/services/telemetry/telemetry_test.go

* Update server/services/telemetry/telemetry_test.go

Co-authored-by: Hossein <hahmadia@users.noreply.github.com>
Co-authored-by: Scott Bishel <scott.bishel@mattermost.com>

server/services/telemetry/telemetry_test.go

@@ -0,0 +1,113 @@
+package telemetry
+
+import (
+	"bytes"
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/mattermost/mattermost-server/v6/shared/mlog"
+	"github.com/stretchr/testify/require"
+)
+
+func mockServer() (chan []byte, *httptest.Server) {
+	done := make(chan []byte, 1)
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		buf := bytes.NewBuffer(nil)
+		if _, err := io.Copy(buf, r.Body); err != nil {
+			panic(err)
+		}
+
+		var v interface{}
+		err := json.Unmarshal(buf.Bytes(), &v)
+		if err != nil {
+			panic(err)
+		}
+
+		b, err := json.MarshalIndent(v, "", "  ")
+		if err != nil {
+			panic(err)
+		}
+
+		// filter the identify message
+		if strings.Contains(string(b), `"type": "identify"`) {
+			return
+		}
+
+		done <- b
+	}))
+
+	return done, server
+}
+
+func TestTelemetry(t *testing.T) {
+	receiveChan, server := mockServer()
+
+	os.Setenv("RUDDER_KEY", "mock-test-rudder-key")
+	os.Setenv("RUDDER_DATAPLANE_URL", server.URL)
+
+	checkMockRudderServer := func(t *testing.T) {
+		// check mock rudder server got
+		got := string(<-receiveChan)
+		require.Contains(t, got, "mockTrackerKey")
+		require.Contains(t, got, "mockTrackerValue")
+	}
+
+	t.Run("Register tracker and run telemetry job", func(t *testing.T) {
+		service := New("mockTelemetryID", mlog.CreateConsoleTestLogger(false, mlog.LvlDebug))
+		service.RegisterTracker("mockTracker", func() (Tracker, error) {
+			return map[string]interface{}{
+				"mockTrackerKey": "mockTrackerValue",
+			}, nil
+		})
+
+		service.RunTelemetryJob(time.Now().UnixNano() / int64(time.Millisecond))
+		checkMockRudderServer(t)
+	})
+
+	t.Run("do telemetry if needed", func(t *testing.T) {
+		service := New("mockTelemetryID", mlog.CreateConsoleTestLogger(false, mlog.LvlDebug))
+		service.RegisterTracker("mockTracker", func() (Tracker, error) {
+			return map[string]interface{}{
+				"mockTrackerKey": "mockTrackerValue",
+			}, nil
+		})
+
+		firstRun := time.Now()
+		t.Run("Send once every 10 minutes for the first hour", func(t *testing.T) {
+			service.doTelemetryIfNeeded(firstRun.Add(-30 * time.Minute))
+			checkMockRudderServer(t)
+		})
+
+		t.Run("Send once every hour thereafter for the first 12 hours", func(t *testing.T) {
+			// firstRun is 2 hours ago and timestampLastTelemetrySent is hour ago
+			// need to do telemetry
+			service.timestampLastTelemetrySent = time.Now().Add(-time.Hour)
+			service.doTelemetryIfNeeded(firstRun.Add(-2 * time.Hour))
+			checkMockRudderServer(t)
+
+			// firstRun is 2 hours ago and timestampLastTelemetrySent is just now
+			// no need to do telemetry
+			service.doTelemetryIfNeeded(firstRun.Add(-2 * time.Hour))
+			require.Equal(t, 0, len(receiveChan))
+		})
+		t.Run("Send at the 24 hour mark and every 24 hours after", func(t *testing.T) {
+			// firstRun is 24 hours ago and timestampLastTelemetrySent is 24 hours ago
+			// need to do telemetry
+			service.timestampLastTelemetrySent = time.Now().Add(-24 * time.Hour)
+			service.doTelemetryIfNeeded(firstRun.Add(-24 * time.Hour))
+			checkMockRudderServer(t)
+
+			// firstRun is 24 hours ago and timestampLastTelemetrySent is just now
+			// no need to do telemetry
+			service.doTelemetryIfNeeded(firstRun.Add(-24 * time.Hour))
+			require.Equal(t, 0, len(receiveChan))
+		})
+	})
+}