Function TestFallbackPollSkipsWhenRecentlyScanned

agent/agentgit/agentgit_test.go:1613–1668

TestFallbackPollSkipsWhenRecentlyScanned pins the RunLoop optimization that swallows a fallback tick when a trigger-driven scan already covered the last fallback interval. Without the skip, a busy chat (agent editing + PathStore notifications) would pay the full fallback scan cost on top of trigger-

(t *testing.T)

// (agent editing + PathStore notifications) would pay the full fallback
// scan cost on top of trigger-driven scans.
func TestFallbackPollSkipsWhenRecentlyScanned(t *testing.T) {
	t.Parallel()

	ctx := testutil.Context(t, testutil.WaitLong)
	repoDir := initTestRepo(t)
	mClock := quartz.NewMock(t)

	ps := agentgit.NewPathStore()
	chatID := uuid.New()

	require.NoError(t, os.WriteFile(filepath.Join(repoDir, "a.go"), []byte("package a\n"), 0o600))
	ps.AddPaths([]uuid.UUID{chatID}, []string{filepath.Join(repoDir, "a.go")})

	stream := dialGitWatchWithPathStore(t, ps, chatID, agentgit.WithClock(mClock))
	ch := stream.Chan()

	// Consume the initial scan from subscribe.
	msg1 := recvMsg(ctx, t, ch)
	require.Equal(t, codersdk.WorkspaceAgentGitServerMessageTypeChanges, msg1.Type)

	// A trigger-driven scan within the fallback interval should
	// cause the next fallback tick to be skipped. Advance part-way
	// to the 5s tick, fire a notification to trigger a scan, then
	// advance the rest of the way to the tick. The tick should be
	// swallowed because lastScanAt is recent.
	mClock.Advance(4 * time.Second).MustWait(context.Background())
	require.NoError(t, os.WriteFile(filepath.Join(repoDir, "a.go"), []byte("package a\n// edit\n"), 0o600))
	ps.Notify([]uuid.UUID{chatID})

	// Consume the trigger-driven scan. lastScanAt is now ~t=4s.
	msg2 := recvMsg(ctx, t, ch)
	require.Equal(t, codersdk.WorkspaceAgentGitServerMessageTypeChanges, msg2.Type)

	// Dirty the tree further so the fallback tick would have
	// something to emit if it were not skipped.
	require.NoError(t, os.WriteFile(filepath.Join(repoDir, "b.go"), []byte("package b\n"), 0o600))

	// Advance to the 5s ticker boundary. The tick fires but is
	// skipped because Since(lastScanAt) = 1s < fallbackPollInterval.
	mClock.Advance(1 * time.Second).MustWait(context.Background())

	// Confirm no scan arrived for the skipped tick.
	select {
	case msg := <-ch:
		t.Fatalf("unexpected scan after skipped fallback tick: %+v", msg)
	case <-time.After(testutil.IntervalFast):
	}

	// Advance to the next ticker boundary (t=10s). lastScanAt is
	// ~4s, so Since = 6s >= fallbackPollInterval and the tick
	// should no longer be skipped.
	mClock.Advance(5 * time.Second).MustWait(context.Background())

	msg3 := recvMsg(ctx, t, ch)
	require.Equal(t, codersdk.WorkspaceAgentGitServerMessageTypeChanges, msg3.Type)
}