test(components/core): add test harness utility

libs/components/core/testing/src/public-api.ts

@@ -10,6 +10,7 @@ export {
 } from './resize-observer-mock';
 export { SkyComponentHarness } from './shared/component-harness';
 export { SkyHarnessFilters } from './shared/harness-filters';
+export { SkyHarnessUtility } from './shared/harness-utility';
 export { SkyQueryableComponentHarness } from './shared/queryable-component-harness';
 export { SkyHelpTestingController } from './help/help-testing-controller';
 export { SkyHelpTestingModule } from './help/help-testing.module';

libs/components/core/testing/src/shared/harness-utility.spec.ts

@@ -0,0 +1,40 @@
+import { TestElement } from '@angular/cdk/testing';
+
+import { SkyHarnessUtility } from './harness-utility';
+
+describe('Harness utility', () => {
+  async function validate(
+    imageCss: string,
+    imageUrl: string | undefined,
+  ): Promise<void> {
+    const el: Partial<TestElement> = {
+      getCssValue: async (property) => {
+        if (property === 'background-image') {
+          return Promise.resolve(imageCss);
+        }
+
+        return '';
+      },
+    };
+
+    await expectAsync(
+      SkyHarnessUtility.getBackgroundImageUrl(el as TestElement),
+    ).toBeResolvedTo(imageUrl);
+  }
+
+  it('should get the background image of a test element', async () => {
+    await validate(
+      `url('https://example.com/bg.png')`,
+      'https://example.com/bg.png',
+    );
+
+    await validate(
+      'url("https://example.com/bg.png")',
+      'https://example.com/bg.png',
+    );
+
+    await validate('url("blob:example.com/abc")', 'blob:example.com/abc');
+
+    await validate('', undefined);
+  });
+});

libs/components/core/testing/src/shared/harness-utility.ts

@@ -0,0 +1,11 @@
+import { TestElement } from '@angular/cdk/testing';
+
+export class SkyHarnessUtility {
+  public static async getBackgroundImageUrl(
+    el: TestElement,
+  ): Promise<string | undefined> {
+    const backgroundImage = await el.getCssValue('background-image');
+
+    return /url\(('|")([^'"]+)('|")\)/gi.exec(backgroundImage)?.[2];
+  }
+}