replace getSelectorForContent with getHarnessLoaderForContent

src/cdk/testing/component-harness.ts

@@ -143,6 +143,29 @@ export interface LocatorFactory {
   locatorForAll<T extends ComponentHarness>(
       harnessType: ComponentHarnessConstructor<T> | HarnessPredicate<T>): AsyncFactoryFn<T[]>;
 
+  /**
+   * Gets a `HarnessLoader` instance for an element under the root of this `LocatorFactory`.
+   * @param selector The selector for the root element.
+   * @return A `HarnessLoader` rooted at the first element matching the given selector.
+   * @throws If no matching element is found for the given selector.
+   */
+  harnessLoaderFor(selector: string): Promise<HarnessLoader>;
+
+  /**
+   * Gets a `HarnessLoader` instance for an element under the root of this `LocatorFactory`
+   * @param selector The selector for the root element.
+   * @return A `HarnessLoader` rooted at the first element matching the given selector, or null if
+   *     no matching element is found.
+   */
+  harnessLoaderForOptional(selector: string): Promise<HarnessLoader | null>;
+
+  /**
+   * Gets a list of `HarnessLoader` instances, one for each matching element.
+   * @param selector The selector for the root element.
+   * @return A list of `HarnessLoader`, one rooted at each element matching the given selector.
+   */
+  harnessLoaderForAll(selector: string): Promise<HarnessLoader[]>;
+
   /**
    * Flushes change detection and async tasks.
    * In most cases it should not be necessary to call this manually. However, there may be some edge

src/cdk/testing/harness-environment.ts

@@ -82,6 +82,23 @@ export abstract class HarnessEnvironment<E> implements HarnessLoader, LocatorFac
     };
   }
 
+  // Implemented as part of the `LocatorFactory` interface.
+  async harnessLoaderFor(selector: string): Promise<HarnessLoader> {
+    return this.createEnvironment(await this._assertElementFound(selector));
+  }
+
+  // Implemented as part of the `LocatorFactory` interface.
+  async harnessLoaderForOptional(selector: string): Promise<HarnessLoader | null> {
+    const elements = await this.getAllRawElements(selector);
+    return elements[0] && this.createEnvironment(elements[0]);
+  }
+
+  // Implemented as part of the `LocatorFactory` interface.
+  async harnessLoaderForAll(selector: string): Promise<HarnessLoader[]> {
+    const elements = await this.getAllRawElements(selector);
+    return elements.map(element => this.createEnvironment(element));
+  }
+
   // Implemented as part of the `HarnessLoader` interface.
   getHarness<T extends ComponentHarness>(
       harnessType: ComponentHarnessConstructor<T> | HarnessPredicate<T>): Promise<T> {

src/material/tabs/testing/shared.spec.ts

@@ -1,5 +1,5 @@
 import {expectAsyncError} from '@angular/cdk/private/testing';
-import {HarnessLoader} from '@angular/cdk/testing';
+import {ComponentHarness, HarnessLoader} from '@angular/cdk/testing';
 import {TestbedHarnessEnvironment} from '@angular/cdk/testing/testbed';
 import {Component} from '@angular/core';
 import {ComponentFixture, TestBed} from '@angular/core/testing';
@@ -96,12 +96,12 @@ export function runHarnessTests(
     expect(await tabs[2].getAriaLabelledby()).toBe('tabLabelId');
   });
 
-  it('should be able to get content element of active tab', async () => {
+  it('should be able to get harness loader for content element of active tab', async () => {
     const tabGroup = await loader.getHarness(tabGroupHarness);
     const tabs = await tabGroup.getTabs();
-    const contentSelector = await tabs[0].getSelectorForContent();
-    const contentEl = document.querySelector(contentSelector) as HTMLElement;
-    expect(contentEl.innerText.trim()).toBe('Content 1');
+    const tabContentLoader = await tabs[0].getHarnessLoaderForContent();
+    const tabContentHarness = await tabContentLoader.getHarness(TestTabContentHarness);
+    expect(await (await tabContentHarness.host()).text()).toBe('Content 1');
   });
 
   it('should be able to get disabled state of tab', async () => {
@@ -153,15 +153,23 @@ export function runHarnessTests(
 @Component({
   template: `
     <mat-tab-group>
-      <mat-tab label="First" aria-label="First tab">Content 1</mat-tab>
-      <mat-tab label="Second" aria-label="Second tab">Content 2</mat-tab>
+      <mat-tab label="First" aria-label="First tab">
+        <span class="test-tab-content">Content 1</span>
+      </mat-tab>
+      <mat-tab label="Second" aria-label="Second tab">
+        <span class="test-tab-content">Content 2</span>
+      </mat-tab>
       <mat-tab label="Third" aria-labelledby="tabLabelId" [disabled]="isDisabled">
         <ng-template matTabLabel>Third</ng-template>
-        Content 3
+        <span class="test-tab-content">Content 3</span>
       </mat-tab>
     </mat-tab-group>
   `
 })
 class TabGroupHarnessTest {
   isDisabled = false;
 }
+
+class TestTabContentHarness extends ComponentHarness {
+  static hostSelector = '.test-tab-content';
+}

src/material/tabs/testing/tab-harness.ts

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {ComponentHarness, HarnessPredicate, TestElement} from '@angular/cdk/testing';
+import {ComponentHarness, HarnessLoader, HarnessPredicate} from '@angular/cdk/testing';
 import {TabHarnessFilters} from './tab-harness-filters';
 
 /**
@@ -25,8 +25,6 @@ export class MatTabHarness extends ComponentHarness {
             (harness, label) => HarnessPredicate.stringMatches(harness.getLabel(), label));
   }
 
-  private _rootLocatorFactory = this.documentRootLocatorFactory();
-
   /** Gets the label of the tab. */
   async getLabel(): Promise<string> {
     return (await this.host()).text();
@@ -62,10 +60,15 @@ export class MatTabHarness extends ComponentHarness {
     await (await this.host()).click();
   }
 
-  /** Gets a selector that can be used to locate the tab's content element. */
-  async getSelectorForContent(): Promise<string> {
+  async getHarnessLoaderForContent(): Promise<HarnessLoader> {
+    const contentId = await this._getContentId();
+    return this.documentRootLocatorFactory().harnessLoaderFor(`#${contentId}`);
+  }
+
+  /** Gets the element id for the content of the current tab. */
+  private async _getContentId(): Promise<string> {
     const hostEl = await this.host();
     // Tabs never have an empty "aria-controls" attribute.
-    return '#' + await hostEl.getAttribute('aria-controls');
+    return (await hostEl.getAttribute('aria-controls'))!;
   }
 }