Test that a late hit and a disabled cache are counted right (closes #56)

A hit served after the request context has ended must still move the hit
count, and a disabled disk cache must report no items and no size even
when its database holds rows from an earlier run.

Model: opus-5-5

internal/imgcache/stats_internal_test.go

@@ -217,6 +217,40 @@ func TestStats_TotalsCountSourcesAndVariants(t *testing.T) {
 	}
 }
 
+// TestStats_DisabledCacheReportsNoItems verifies that a disabled disk cache
+// reports no items and no size, even when its database still holds the
+// rows of an earlier run with the disk cache enabled.
+func TestStats_DisabledCacheReportsNoItems(t *testing.T) {
+	t.Parallel()
+
+	enabled, _ := newEvictionTestCache(t, 1<<30)
+
+	storeEvictionTestSource(t, enabled, testHostCDN, testPathCat,
+		bytes.Repeat([]byte{0xAA}, 1000))
+	storeEvictionTestVariant(t, enabled, testVariantKeyOne,
+		bytes.Repeat([]byte{0xAB}, 500))
+
+	disabled, err := NewCache(enabled.db, CacheConfig{
+		StateDir:         t.TempDir(),
+		CacheTTL:         time.Hour,
+		NegativeTTL:      5 * time.Minute,
+		DisableDiskCache: true,
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	stats, err := disabled.Stats(t.Context())
+	if err != nil {
+		t.Fatalf("Stats() error = %v", err)
+	}
+
+	if stats.TotalItems != 0 || stats.TotalSizeBytes != 0 {
+		t.Errorf("TotalItems = %d, TotalSizeBytes = %d, want 0 and 0",
+			stats.TotalItems, stats.TotalSizeBytes)
+	}
+}
+
 // cacheStatsCounters holds the counters of the cache_stats row, in column
 // order.
 type cacheStatsCounters struct {
@@ -415,3 +449,51 @@ func TestService_Get_CountsInterruptedMisses(t *testing.T) {
 		})
 	}
 }
+
+// TestService_Get_CountsHitAfterRequestEnds checks every cache_stats counter
+// after a hit served with a request context that has already ended: only
+// the hit count moves.
+func TestService_Get_CountsHitAfterRequestEnds(t *testing.T) {
+	t.Parallel()
+
+	svc, fixtures := SetupTestService(t)
+
+	req := &ImageRequest{
+		SourceHost: fixtures.GoodHost,
+		SourcePath: testPathPhoto,
+		Size:       Size{Width: 50, Height: 50},
+		Format:     FormatJPEG,
+		Quality:    85,
+		FitMode:    FitCover,
+	}
+
+	// A first request caches the variant.
+	resp, err := svc.Get(t.Context(), req)
+	if err != nil {
+		t.Fatalf("first Get() error = %v", err)
+	}
+
+	_ = resp.Content.Close()
+
+	want := readCacheStatsCounters(t, svc.cache)
+	want.hitCount++
+
+	ctx, cancel := context.WithCancel(t.Context())
+	cancel()
+
+	resp, err = svc.Get(ctx, req)
+	if err != nil {
+		t.Fatalf("Get() with an ended request context: error = %v", err)
+	}
+
+	_ = resp.Content.Close()
+
+	if resp.CacheStatus != CacheHit {
+		t.Fatalf("CacheStatus = %v, want %v", resp.CacheStatus, CacheHit)
+	}
+
+	got := readCacheStatsCounters(t, svc.cache)
+	if got != want {
+		t.Errorf("counters = %+v, want %+v", got, want)
+	}
+}