pixels: do more extensive testing for roundtrip bugs between Set and Get

pixel/image_test.go

@@ -183,22 +183,30 @@ func TestImageFromBytesMonochrome(t *testing.T) {
 // contain the same data afterwards.
 func TestImageNoise(t *testing.T) {
 	t.Run("RGB888", func(t *testing.T) {
-		testImageNoise[pixel.RGB888](t)
+		testImageNoiseN[pixel.RGB888](t)
 	})
 	t.Run("RGB565BE", func(t *testing.T) {
-		testImageNoise[pixel.RGB565BE](t)
+		testImageNoiseN[pixel.RGB565BE](t)
 	})
 	t.Run("RGB555", func(t *testing.T) {
-		testImageNoise[pixel.RGB555](t)
+		testImageNoiseN[pixel.RGB555](t)
 	})
 	t.Run("RGB444BE", func(t *testing.T) {
-		testImageNoise[pixel.RGB444BE](t)
+		testImageNoiseN[pixel.RGB444BE](t)
 	})
 	t.Run("Monochrome", func(t *testing.T) {
-		testImageNoise[pixel.Monochrome](t)
+		testImageNoiseN[pixel.Monochrome](t)
 	})
 }
 
+// Run the testImageNoise multiple times, because a single test might not catch
+// all bugs (since the test uses random data).
+func testImageNoiseN[T pixel.Color](t *testing.T) {
+	for i := 0; i < 10; i++ {
+		testImageNoise[T](t)
+	}
+}
+
 func testImageNoise[T pixel.Color](t *testing.T) {
 	// Create an image of a random width/height for extra testing.
 	width := rand.Int()%500 + 10