feat(material/tabs/testing): polish harness API

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]) : null;
+  }
+
+  // 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/BUILD.bazel

@@ -25,6 +25,7 @@ ng_test_library(
     srcs = ["shared.spec.ts"],
     deps = [
         ":testing",
+        "//src/cdk/private/testing",
         "//src/cdk/testing",
         "//src/cdk/testing/testbed",
         "//src/material/tabs",

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

@@ -1,4 +1,5 @@
-import {HarnessLoader} from '@angular/cdk/testing';
+import {expectAsyncError} from '@angular/cdk/private/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';
@@ -51,6 +52,26 @@ export function runHarnessTests(
     expect(tabs.length).toBe(3);
   });
 
+  it('should be able to get filtered tabs', async () => {
+    const tabGroup = await loader.getHarness(tabGroupHarness);
+    const tabs = await tabGroup.getTabs({label: 'Third'});
+    expect(tabs.length).toBe(1);
+    expect(await tabs[0].getLabel()).toBe('Third');
+  });
+
+  it('should be able to select tab from tab-group', async () => {
+    const tabGroup = await loader.getHarness(tabGroupHarness);
+    expect(await (await tabGroup.getSelectedTab()).getLabel()).toBe('First');
+    await tabGroup.selectTab({label: 'Second'});
+    expect(await (await tabGroup.getSelectedTab()).getLabel()).toBe('Second');
+  });
+
+  it('should throw error when attempting to select invalid tab', async () => {
+    const tabGroup = await loader.getHarness(tabGroupHarness);
+    await expectAsyncError(() => tabGroup.selectTab({label: 'Fake'}),
+        /Error: Cannot find mat-tab matching filter {"label":"Fake"}/);
+  });
+
   it('should be able to get label of tabs', async () => {
     const tabGroup = await loader.getHarness(tabGroupHarness);
     const tabs = await tabGroup.getTabs();
@@ -75,16 +96,13 @@ 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();
-    expect(await (await tabs[0].getContentElement()).text()).toBe('Content 1');
-  });
-
-  it('should be able to get content element of active tab', async () => {
-    const tabGroup = await loader.getHarness(tabGroupHarness);
-    const tabs = await tabGroup.getTabs();
-    expect(await (await tabs[0].getContentElement()).text()).toBe('Content 1');
+    expect(await tabs[0].getTextContent()).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 () => {
@@ -136,15 +154,23 @@ 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-group-harness.ts

@@ -7,7 +7,7 @@
  */
 
 import {ComponentHarness, HarnessPredicate} from '@angular/cdk/testing';
-import {TabGroupHarnessFilters} from './tab-harness-filters';
+import {TabGroupHarnessFilters, TabHarnessFilters} from './tab-harness-filters';
 import {MatTabHarness} from './tab-harness';
 
 /**
@@ -34,11 +34,9 @@ export class MatTabGroupHarness extends ComponentHarness {
         });
   }
 
-  private _tabs = this.locatorForAll(MatTabHarness);
-
   /** Gets all tabs of the tab group. */
-  async getTabs(): Promise<MatTabHarness[]> {
-    return this._tabs();
+  async getTabs(filter: TabHarnessFilters = {}): Promise<MatTabHarness[]> {
+    return this.locatorForAll(MatTabHarness.with(filter))();
   }
 
   /** Gets the selected tab of the tab group. */
@@ -52,4 +50,13 @@ export class MatTabGroupHarness extends ComponentHarness {
     }
     throw new Error('No selected tab could be found.');
   }
+
+  /** Selects a tab in this tab group. */
+  async selectTab(filter: TabHarnessFilters = {}): Promise<void> {
+    const tabs = await this.getTabs(filter);
+    if (!tabs.length) {
+      throw Error(`Cannot find mat-tab matching filter ${JSON.stringify(filter)}`);
+    }
+    await tabs[0].select();
+  }
 }

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

@@ -7,7 +7,9 @@
  */
 import {BaseHarnessFilters} from '@angular/cdk/testing';
 
-export interface TabHarnessFilters extends BaseHarnessFilters {}
+export interface TabHarnessFilters extends BaseHarnessFilters {
+  label?: string | RegExp;
+}
 
 export interface TabGroupHarnessFilters extends BaseHarnessFilters {
   selectedTabLabel?: string | RegExp;

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';
 
 /**
@@ -20,11 +20,11 @@ export class MatTabHarness extends ComponentHarness {
    * Gets a `HarnessPredicate` that can be used to search for a tab with specific attributes.
    */
   static with(options: TabHarnessFilters = {}): HarnessPredicate<MatTabHarness> {
-    return new HarnessPredicate(MatTabHarness, options);
+    return new HarnessPredicate(MatTabHarness, options)
+        .addOption('label', options.label,
+            (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();
@@ -40,15 +40,6 @@ export class MatTabHarness extends ComponentHarness {
     return (await this.host()).getAttribute('aria-labelledby');
   }
 
-  /**
-   * Gets the content element of the given tab. Note that the element will be empty
-   * until the tab is selected. This is an implementation detail of the tab-group
-   * in order to avoid rendering of non-active tabs.
-   */
-  async getContentElement(): Promise<TestElement> {
-    return this._rootLocatorFactory.locatorFor(`#${await this._getContentId()}`)();
-  }
-
   /** Whether the tab is selected. */
   async isSelected(): Promise<boolean> {
     const hostEl = await this.host();
@@ -69,6 +60,22 @@ export class MatTabHarness extends ComponentHarness {
     await (await this.host()).click();
   }
 
+  /** Gets the text content of the tab. */
+  async getTextContent(): Promise<string> {
+    const contentId = await this._getContentId();
+    const contentEl = await this.documentRootLocatorFactory().locatorFor(`#${contentId}`)();
+    return contentEl.text();
+  }
+
+  /**
+   * Gets a `HarnessLoader` that can be used to load harnesses for components within the tab's
+   * content area.
+   */
+  async getHarnessLoaderForContent(): Promise<HarnessLoader> {
+    const contentId = await this._getContentId();
+    return this.documentRootLocatorFactory().harnessLoaderFor(`#${contentId}`);
+  }
+
   /** Gets the element id for the content of the current tab. */
   private async _getContentId(): Promise<string> {
     const hostEl = await this.host();

tools/public_api_guard/cdk/testing.d.ts

@@ -63,6 +63,9 @@ export declare abstract class HarnessEnvironment<E> implements HarnessLoader, Lo
     getChildLoader(selector: string): Promise<HarnessLoader>;
     protected abstract getDocumentRoot(): E;
     getHarness<T extends ComponentHarness>(harnessType: ComponentHarnessConstructor<T> | HarnessPredicate<T>): Promise<T>;
+    harnessLoaderFor(selector: string): Promise<HarnessLoader>;
+    harnessLoaderForAll(selector: string): Promise<HarnessLoader[]>;
+    harnessLoaderForOptional(selector: string): Promise<HarnessLoader | null>;
     locatorFor<T extends ComponentHarness>(harnessType: ComponentHarnessConstructor<T> | HarnessPredicate<T>): AsyncFactoryFn<T>;
     locatorFor(selector: string): AsyncFactoryFn<TestElement>;
     locatorForAll<T extends ComponentHarness>(harnessType: ComponentHarnessConstructor<T> | HarnessPredicate<T>): AsyncFactoryFn<T[]>;
@@ -96,10 +99,13 @@ export interface LocatorFactory {
     rootElement: TestElement;
     documentRootLocatorFactory(): LocatorFactory;
     forceStabilize(): Promise<void>;
-    locatorFor(selector: string): AsyncFactoryFn<TestElement>;
+    harnessLoaderFor(selector: string): Promise<HarnessLoader>;
+    harnessLoaderForAll(selector: string): Promise<HarnessLoader[]>;
+    harnessLoaderForOptional(selector: string): Promise<HarnessLoader | null>;
     locatorFor<T extends ComponentHarness>(harnessType: ComponentHarnessConstructor<T> | HarnessPredicate<T>): AsyncFactoryFn<T>;
-    locatorForAll(selector: string): AsyncFactoryFn<TestElement[]>;
+    locatorFor(selector: string): AsyncFactoryFn<TestElement>;
     locatorForAll<T extends ComponentHarness>(harnessType: ComponentHarnessConstructor<T> | HarnessPredicate<T>): AsyncFactoryFn<T[]>;
+    locatorForAll(selector: string): AsyncFactoryFn<TestElement[]>;
     locatorForOptional(selector: string): AsyncFactoryFn<TestElement | null>;
     locatorForOptional<T extends ComponentHarness>(harnessType: ComponentHarnessConstructor<T> | HarnessPredicate<T>): AsyncFactoryFn<T | null>;
 }