[ImageLoader] Add unit tests for getSize

Author: lkinasiewicz

packages/react-native-web/src/modules/ImageLoader/__tests__/index-test.js

@@ -0,0 +1,69 @@
+import ImageLoader from '../index';
+
+const testImage =
+  'data:image/webp;base64,UklGRkYAAABXRUJQVlA4IDoAAADwAgCdASoXABMAPi0QhkKhoQ36AAwBYllAHYAAajokAAD+/SFF//G83mta3//9QZ/5Bn/kGfp4AAAA';
+const testImageWidth = 23;
+const testImageHeight = 19;
+
+const DefaultImage = window.Image;
+
+describe('ImageLoader', () => {
+  afterEach(() => {
+    window.Image = DefaultImage;
+  });
+
+  test('Success callback is called when image loads', async () => {
+    window.Image = MockImage;
+    const successCallback = jest.fn();
+    const failureCallback = jest.fn();
+    ImageLoader.getSize(testImage, successCallback, failureCallback);
+    await jest.runAllTimers();
+    expect(failureCallback).toHaveBeenCalledTimes(0);
+    expect(successCallback).toHaveBeenCalledTimes(1);
+    expect(successCallback).toHaveBeenCalledWith(
+      testImageWidth,
+      testImageHeight
+    );
+  });
+
+  test('Failure callback is called when image fails to load', async () => {
+    window.Image = NotLoadingMockImage;
+    const successCallback = jest.fn();
+    const failureCallback = jest.fn();
+    ImageLoader.getSize(testImage, successCallback, failureCallback);
+    await jest.runAllTimers();
+    expect(failureCallback).toHaveBeenCalledTimes(1);
+    expect(successCallback).toHaveBeenCalledTimes(0);
+  });
+});
+
+class MockImage {
+  constructor(width = 0, height = 0) {
+    this.width = width;
+    this.height = height;
+    this.naturalWidth = 0;
+    this.naturalHeight = 0;
+    this._src = '';
+  }
+  get src() {
+    return this._src;
+  }
+  set src(uri) {
+    this._src = uri;
+    window.setTimeout(this.onload, 0);
+  }
+  decode() {
+    this.naturalWidth = testImageWidth;
+    this.naturalHeight = testImageHeight;
+    return Promise.resolve();
+  }
+  onerror() {}
+  onload() {}
+}
+
+class NotLoadingMockImage extends MockImage {
+  set src(uri) {
+    this._src = uri;
+    window.setTimeout(this.onerror, 0);
+  }
+}