test: heartbeats are stamped with the application clock, not the database's NOW() (#51), red

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

internal/progress/tracker_test.go

@@ -17,11 +17,12 @@ import (
 
 // fakeSink records every saved snapshot and every heartbeat.
 type fakeSink struct {
-	mu    sync.Mutex
-	saves [][]domain.ProgressStep
-	at    []time.Time
-	beats int
-	err   error
+	mu     sync.Mutex
+	saves  [][]domain.ProgressStep
+	at     []time.Time
+	beats  int
+	beatAt []time.Time
+	err    error
 }
 
 func (f *fakeSink) SaveProgress(_ context.Context, steps []domain.ProgressStep, at time.Time) error {
@@ -32,10 +33,11 @@ func (f *fakeSink) SaveProgress(_ context.Context, steps []domain.ProgressStep,
 	return f.err
 }
 
-func (f *fakeSink) Beat(context.Context) error {
+func (f *fakeSink) Beat(_ context.Context, at time.Time) error {
 	f.mu.Lock()
 	defer f.mu.Unlock()
 	f.beats++
+	f.beatAt = append(f.beatAt, at)
 	return f.err
 }
 
@@ -297,7 +299,7 @@ func (r *retainingSink) SaveProgress(_ context.Context, steps []domain.ProgressS
 	r.got = append(r.got, steps)
 	return nil
 }
-func (r *retainingSink) Beat(context.Context) error { return nil }
+func (r *retainingSink) Beat(context.Context, time.Time) error { return nil }
 
 func TestTracker_ASnapshotHandedToTheSinkIsNotChangedByLaterTransitions(t *testing.T) {
 	sink := &retainingSink{}
@@ -400,3 +402,20 @@ func TestTracker_AnnotateAttachesANoteToAStepAndSavesItAtOnce(t *testing.T) {
 	require.Equal(t, "20 min of the 79 the file claimed", sink.last(t)[0].Note)
 	require.NotPanics(t, func() { tr.Annotate("no-such-step", "x") })
 }
+
+func TestTracker_BeatIsStampedWithTheTrackersClock(t *testing.T) {
+	// alive_at used the database's NOW() while the page compared it with the application
+	// clock; a skewed database clock showed a healthy job as lost (#51).
+	tr, sink, clk, _ := newTracker(t)
+	clk.tick(42 * time.Second)
+	want := clk.now()
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	go tr.Heartbeat(ctx, 5*time.Millisecond, time.Hour)
+
+	require.Eventually(t, func() bool { return sink.beatCount() >= 1 }, 2*time.Second, 5*time.Millisecond)
+	sink.mu.Lock()
+	defer sink.mu.Unlock()
+	require.True(t, sink.beatAt[0].Equal(want), "beat stamped %v, the tracker's clock says %v", sink.beatAt[0], want)
+}