Fixing matching:TestCheckIdleTaskList test flackiness

For some reason it almost always fails in IDE (4/5 cases, goland),
but passes in console. At the same time, the test clearly had issues:
 - it's been 3 subtests in one
 - only the first subtest checked task-list became stopped when unused
 - the third subtest (the one which has been failing) never succeeded
   with `tlm.AddTask` since writer never started - instead of tlm.Start()
   we used special version which supposed to mimic it, but never started
   the writer.

The test is still problematic since it continues using time.Sleep all
around, but so do all the other tests for matching :-(

More comments and error-messages also bring more clarity to what the
test is actually for.

service/matching/taskListManager_test.go

@@ -23,7 +23,6 @@ package matching
 import (
 	"context"
 	"sync"
-	"sync/atomic"
 	"testing"
 	"time"
 
@@ -219,68 +218,78 @@ func TestDescribeTaskList(t *testing.T) {
 	require.Zero(t, taskListStatus.GetBacklogCountHint())
 }
 
-func tlMgrStartWithoutNotifyEvent(tlm *taskListManagerImpl) {
-	// mimic tlm.Start() but avoid calling notifyEvent
-	tlm.liveness.Start()
-	tlm.startWG.Done()
-	go tlm.taskReader.dispatchBufferedTasks(defaultTaskBufferIsolationGroup)
-	go tlm.taskReader.getTasksPump()
-}
-
 func TestCheckIdleTaskList(t *testing.T) {
-	controller := gomock.NewController(t)
-	logger := testlogger.New(t)
-
 	cfg := NewConfig(dynamicconfig.NewNopCollection(), "some random hostname")
 	cfg.IdleTasklistCheckInterval = dynamicconfig.GetDurationPropertyFnFilteredByTaskListInfo(10 * time.Millisecond)
+	logger := testlogger.New(t)
 
-	// Idle
-	tlm := createTestTaskListManagerWithConfig(logger, controller, cfg)
-	tlMgrStartWithoutNotifyEvent(tlm)
-	time.Sleep(20 * time.Millisecond)
-	require.False(t, atomic.CompareAndSwapInt32(&tlm.stopped, 0, 1))
-
-	// Active poll-er
-	tlm = createTestTaskListManagerWithConfig(logger, controller, cfg)
-	tlMgrStartWithoutNotifyEvent(tlm)
-	time.Sleep(8 * time.Millisecond)
-	ctx, cancel := context.WithTimeout(context.Background(), time.Microsecond)
-	_, _ = tlm.GetTask(ctx, nil)
-	cancel()
-	time.Sleep(6 * time.Millisecond)
-	require.Equal(t, int32(0), tlm.stopped)
-	tlm.Stop()
-	require.Equal(t, int32(1), tlm.stopped)
+	t.Run("Idle task-list", func(t *testing.T) {
+		ctrl := gomock.NewController(t)
+		tlm := createTestTaskListManagerWithConfig(logger, ctrl, cfg)
+		require.NoError(t, tlm.Start())
 
-	// Active adding task
-	domainID := uuid.New()
-	workflowID := "some random workflowID"
-	runID := "some random runID"
+		require.Equal(t, int32(0), tlm.stopped, "idle check interval had not passed yet")
+		time.Sleep(20 * time.Millisecond)
+		require.Equal(t, int32(1), tlm.stopped, "idle check interval should have pass")
+	})
 
-	addTaskParam := addTaskParams{
-		execution: &types.WorkflowExecution{
-			WorkflowID: workflowID,
-			RunID:      runID,
-		},
-		taskInfo: &persistence.TaskInfo{
-			DomainID:               domainID,
-			WorkflowID:             workflowID,
-			RunID:                  runID,
-			ScheduleID:             2,
-			ScheduleToStartTimeout: 5,
-			CreatedTime:            time.Now(),
-		},
-	}
-	tlm = createTestTaskListManagerWithConfig(logger, controller, cfg)
-	tlMgrStartWithoutNotifyEvent(tlm)
-	time.Sleep(8 * time.Millisecond)
-	ctx, cancel = context.WithTimeout(context.Background(), time.Microsecond)
-	_, _ = tlm.AddTask(ctx, addTaskParam)
-	cancel()
-	time.Sleep(6 * time.Millisecond)
-	require.Equal(t, int32(0), tlm.stopped)
-	tlm.Stop()
-	require.Equal(t, int32(1), tlm.stopped)
+	t.Run("Active poll-er", func(t *testing.T) {
+		ctrl := gomock.NewController(t)
+		tlm := createTestTaskListManagerWithConfig(logger, ctrl, cfg)
+		require.NoError(t, tlm.Start())
+
+		time.Sleep(8 * time.Millisecond)
+		ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+		_, _ = tlm.GetTask(ctx, nil)
+		cancel()
+
+		// task list manager should have been stopped,
+		// but GetTask extends auto-stop until the next check-idle-task-list-interval
+		time.Sleep(6 * time.Millisecond)
+		require.Equal(t, int32(0), tlm.stopped)
+
+		time.Sleep(20 * time.Millisecond)
+		require.Equal(t, int32(1), tlm.stopped, "check-idle-task-list definitely passed")
+	})
+
+	t.Run("Active adding task", func(t *testing.T) {
+		domainID := uuid.New()
+		workflowID := uuid.New()
+		runID := uuid.New()
+
+		addTaskParam := addTaskParams{
+			execution: &types.WorkflowExecution{
+				WorkflowID: workflowID,
+				RunID:      runID,
+			},
+			taskInfo: &persistence.TaskInfo{
+				DomainID:               domainID,
+				WorkflowID:             workflowID,
+				RunID:                  runID,
+				ScheduleID:             2,
+				ScheduleToStartTimeout: 5,
+				CreatedTime:            time.Now(),
+			},
+		}
+
+		ctrl := gomock.NewController(t)
+		tlm := createTestTaskListManagerWithConfig(logger, ctrl, cfg)
+		require.NoError(t, tlm.Start())
+
+		time.Sleep(8 * time.Millisecond)
+		ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+		_, err := tlm.AddTask(ctx, addTaskParam)
+		require.NoError(t, err)
+		cancel()
+
+		// task list manager should have been stopped,
+		// but AddTask extends auto-stop until the next check-idle-task-list-interval
+		time.Sleep(6 * time.Millisecond)
+		require.Equal(t, int32(0), tlm.stopped)
+
+		time.Sleep(20 * time.Millisecond)
+		require.Equal(t, int32(1), tlm.stopped, "check-idle-task-list definitely passed")
+	})
 }
 
 func TestAddTaskStandby(t *testing.T) {
@@ -291,7 +300,8 @@ func TestAddTaskStandby(t *testing.T) {
 	cfg.IdleTasklistCheckInterval = dynamicconfig.GetDurationPropertyFnFilteredByTaskListInfo(10 * time.Millisecond)
 
 	tlm := createTestTaskListManagerWithConfig(logger, controller, cfg)
-	tlMgrStartWithoutNotifyEvent(tlm)
+	require.NoError(t, tlm.Start())
+
 	// stop taskWriter so that we can check if there's any call to it
 	// otherwise the task persist process is async and hard to test
 	tlm.taskWriter.Stop()