createTestImage function Null safety

Future<Image> createTestImage (
  1. {int width: 1,
  2. int height: 1,
  3. bool cache: true}

Creates an arbitrarily sized image for testing.

If the cache parameter is set to true, the image will be cached for the rest of this suite. This is normally desirable, assuming a test suite uses images with the same dimensions in most tests, as it will save on memory usage and CPU time over the course of the suite. However, it should be avoided for images that are used only once in a test suite, especially if the image is large, as it will require holding on to the memory for that image for the duration of the suite.

This method requires real async work, and will not work properly in the FakeAsync zones set up by testWidgets. Typically, it should be invoked as a setup step before testWidgets are run, such as setUp or setUpAll. If needed, it can be invoked using WidgetTester.runAsync.


Future<ui.Image> createTestImage({
  int width = 1,
  int height = 1,
  bool cache = true,
}) => TestAsyncUtils.guard(() async {
  assert(width != null && width > 0);
  assert(height != null && height > 0);
  assert(cache != null);

  final int cacheKey = hashValues(width, height);
  if (cache && _cache.containsKey(cacheKey)) {
    return _cache[cacheKey]!.clone();

  final ui.Image image = await _createImage(width, height);
  if (cache) {
    _cache[cacheKey] = image.clone();
  return image;