feat(material-experimental): add test harness for snack-bar

.github/CODEOWNERS

@@ -105,6 +105,7 @@
 /src/material-experimental/mdc-slide-toggle/**     @crisbeto
 # Note to implementer: please repossess
 /src/material-experimental/mdc-slider/**           @devversion
+/src/material-experimental/mdc-snack-bar/**        @devversion
 /src/material-experimental/mdc-tabs/**             @crisbeto
 /src/material-experimental/mdc-sidenav/**          @crisbeto
 /src/material-experimental/mdc-theming/**          @mmalerba

src/cdk-experimental/testing/testbed/testbed-harness-environment.ts

@@ -14,7 +14,7 @@ import {UnitTestElement} from './unit-test-element';
 
 /** A `HarnessEnvironment` implementation for Angular's Testbed. */
 export class TestbedHarnessEnvironment extends HarnessEnvironment<Element> {
-  protected constructor(rawRootElement: Element, private _fixture: ComponentFixture<unknown>) {
+  constructor(rawRootElement: Element, private _fixture: ComponentFixture<unknown>) {
     super(rawRootElement);
   }
 

src/material-experimental/mdc-snack-bar/harness/BUILD.bazel

@@ -0,0 +1,31 @@
+package(default_visibility = ["//visibility:public"])
+
+load("//tools:defaults.bzl", "ng_test_library", "ng_web_test_suite", "ts_library")
+
+ts_library(
+    name = "harness",
+    srcs = glob(
+        ["**/*.ts"],
+        exclude = ["**/*.spec.ts"],
+    ),
+    deps = [
+        "//src/cdk-experimental/testing",
+    ],
+)
+
+ng_test_library(
+    name = "harness_tests",
+    srcs = glob(["**/*.spec.ts"]),
+    deps = [
+        ":harness",
+        "//src/cdk-experimental/testing",
+        "//src/cdk-experimental/testing/testbed",
+        "//src/material/snack-bar",
+        "@npm//@angular/platform-browser",
+    ],
+)
+
+ng_web_test_suite(
+    name = "tests",
+    deps = [":harness_tests"],
+)

src/material-experimental/mdc-snack-bar/harness/snack-bar-harness.spec.ts

@@ -0,0 +1,168 @@
+import {HarnessLoader} from '@angular/cdk-experimental/testing';
+import {TestbedHarnessEnvironment} from '@angular/cdk-experimental/testing/testbed';
+import {Component, TemplateRef, ViewChild} from '@angular/core';
+import {ComponentFixture, TestBed} from '@angular/core/testing';
+import {MatSnackBar, MatSnackBarConfig, MatSnackBarModule} from '@angular/material/snack-bar';
+import {NoopAnimationsModule} from '@angular/platform-browser/animations';
+import {MatSnackBarHarness} from './snack-bar-harness';
+
+let fixture: ComponentFixture<SnackbarHarnessTest>;
+let loader: HarnessLoader;
+let snackBarHarness: typeof MatSnackBarHarness;
+
+describe('MatSnackBarHarness', () => {
+  describe('non-MDC-based', () => {
+    beforeEach(async () => {
+      await TestBed
+          .configureTestingModule({
+            imports: [MatSnackBarModule, NoopAnimationsModule],
+            declarations: [SnackbarHarnessTest],
+          })
+          .compileComponents();
+
+      fixture = TestBed.createComponent(SnackbarHarnessTest);
+      fixture.detectChanges();
+      // Note: we need to specify "document.body" as root element because
+      // the snack-bar's will be added as immediate children of the body.
+      loader = new TestbedHarnessEnvironment(document.body, fixture);
+      snackBarHarness = MatSnackBarHarness;
+    });
+
+    runTests();
+  });
+
+  describe(
+      'MDC-based',
+      () => {
+          // TODO: run tests for MDC based snack-bar once implemented.
+      });
+});
+
+/** Shared tests to run on both the original and MDC-based snack-bar's. */
+function runTests() {
+  it('should load harness for simple snack-bar', async () => {
+    const snackBarRef = fixture.componentInstance.openSimple('Hello!', '');
+    let snackBars = await loader.getAllHarnesses(snackBarHarness);
+
+    expect(snackBars.length).toBe(1);
+
+    snackBarRef.dismiss();
+    snackBars = await loader.getAllHarnesses(snackBarHarness);
+    expect(snackBars.length).toBe(0);
+  });
+
+  it('should load harness for custom snack-bar', async () => {
+    const snackBarRef = fixture.componentInstance.openCustom();
+    let snackBars = await loader.getAllHarnesses(snackBarHarness);
+
+    expect(snackBars.length).toBe(1);
+
+    snackBarRef.dismiss();
+    snackBars = await loader.getAllHarnesses(snackBarHarness);
+    expect(snackBars.length).toBe(0);
+  });
+
+  it('should be able to get role of snack-bar', async () => {
+    fixture.componentInstance.openCustom();
+    let snackBar = await loader.getHarness(snackBarHarness);
+    expect(await snackBar.getRole()).toBe('alert');
+
+    fixture.componentInstance.openCustom({politeness: 'polite'});
+    snackBar = await loader.getHarness(snackBarHarness);
+    expect(await snackBar.getRole()).toBe('status');
+
+    fixture.componentInstance.openCustom({politeness: 'off'});
+    snackBar = await loader.getHarness(snackBarHarness);
+    expect(await snackBar.getRole()).toBe(null);
+  });
+
+  it('should be able to get message of simple snack-bar', async () => {
+    fixture.componentInstance.openSimple('Subscribed to newsletter.');
+    let snackBar = await loader.getHarness(snackBarHarness);
+    expect(await snackBar.getMessage()).toBe('Subscribed to newsletter.');
+
+    // For snack-bar's with custom template, the message cannot be
+    // retrieved. We expect an error to be thrown.
+    fixture.componentInstance.openCustom();
+    snackBar = await loader.getHarness(snackBarHarness);
+    await expectAsyncError(() => snackBar.getMessage(), /custom content/);
+  });
+
+  it('should be able to get action description of simple snack-bar', async () => {
+    fixture.componentInstance.openSimple('Hello', 'Unsubscribe');
+    let snackBar = await loader.getHarness(snackBarHarness);
+    expect(await snackBar.getActionDescription()).toBe('Unsubscribe');
+
+    // For snack-bar's with custom template, the action description
+    // cannot be retrieved. We expect an error to be thrown.
+    fixture.componentInstance.openCustom();
+    snackBar = await loader.getHarness(snackBarHarness);
+    await expectAsyncError(() => snackBar.getActionDescription(), /custom content/);
+  });
+
+  it('should be able to check whether simple snack-bar has action', async () => {
+    fixture.componentInstance.openSimple('With action', 'Unsubscribe');
+    let snackBar = await loader.getHarness(snackBarHarness);
+    expect(await snackBar.hasAction()).toBe(true);
+
+    fixture.componentInstance.openSimple('No action');
+    snackBar = await loader.getHarness(snackBarHarness);
+    expect(await snackBar.hasAction()).toBe(false);
+
+    // For snack-bar's with custom template, the action cannot
+    // be found. We expect an error to be thrown.
+    fixture.componentInstance.openCustom();
+    snackBar = await loader.getHarness(snackBarHarness);
+    await expectAsyncError(() => snackBar.hasAction(), /custom content/);
+  });
+
+  it('should be able to dismiss simple snack-bar with action', async () => {
+    const snackBarRef = fixture.componentInstance.openSimple('With action', 'Unsubscribe');
+    let snackBar = await loader.getHarness(snackBarHarness);
+    let actionCount = 0;
+    snackBarRef.onAction().subscribe(() => actionCount++);
+
+    await snackBar.dismissWithAction();
+    expect(actionCount).toBe(1);
+
+    fixture.componentInstance.openSimple('No action');
+    snackBar = await loader.getHarness(snackBarHarness);
+    await expectAsyncError(() => snackBar.dismissWithAction(), /without action/);
+  });
+}
+
+/**
+ * Expects the asynchronous function to throw an error that matches
+ * the specified expectation.
+ */
+async function expectAsyncError(fn: () => Promise<any>, expectation: RegExp) {
+  let error: string|null = null;
+  try {
+    await fn();
+  } catch (e) {
+    error = e.toString();
+  }
+  expect(error).not.toBe(null);
+  expect(error!).toMatch(expectation);
+}
+
+@Component({
+  template: `
+    <ng-template>
+      My custom snack-bar.
+    </ng-template>
+  `
+})
+class SnackbarHarnessTest {
+  @ViewChild(TemplateRef, {static: false}) customTmpl: TemplateRef<any>;
+
+  constructor(readonly snackBar: MatSnackBar) {}
+
+  openSimple(message: string, action = '', config?: MatSnackBarConfig) {
+    return this.snackBar.open(message, action, config);
+  }
+
+  openCustom(config?: MatSnackBarConfig) {
+    return this.snackBar.openFromTemplate(this.customTmpl, config);
+  }
+}

src/material-experimental/mdc-snack-bar/harness/snack-bar-harness.ts

@@ -0,0 +1,95 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {ComponentHarness} from '@angular/cdk-experimental/testing';
+
+/**
+ * Harness for interacting with a standard mat-snack-bar in tests.
+ * @dynamic
+ */
+export class MatSnackBarHarness extends ComponentHarness {
+  // Developers can provide a custom component or template for the
+  // snackbar. The canonical snack-bar parent is the "MatSnackBarContainer".
+  static hostSelector = '.mat-snack-bar-container';
+
+  private _simpleSnackBar = this.locatorForOptional('.mat-simple-snackbar');
+  private _simpleSnackBarMessage = this.locatorFor('.mat-simple-snackbar > span');
+  private _simpleSnackBarActionButton =
+      this.locatorForOptional('.mat-simple-snackbar-action > button');
+
+  /**
+   * Gets the role of the snack-bar. The role of a snack-bar is determined based
+   * on the ARIA politeness specified in the snack-bar config.
+   */
+  async getRole(): Promise<'alert'|'status'|null> {
+    return (await this.host()).getAttribute('role') as Promise<'alert'|'status'|null>;
+  }
+
+  /**
+   * Gets whether the snack-bar has an action. Method cannot be
+   * used for snack-bar's with custom content.
+   */
+  async hasAction(): Promise<boolean> {
+    await this._assertSimpleSnackBar();
+    return (await this._simpleSnackBarActionButton()) !== null;
+  }
+
+  /**
+   * Gets the description of the snack-bar. Method cannot be
+   * used for snack-bar's without action or with custom content.
+   */
+  async getActionDescription(): Promise<string> {
+    await this._assertSimpleSnackBarWithAction();
+    return (await this._simpleSnackBarActionButton())!.text();
+  }
+
+
+  /**
+   * Dismisses the snack-bar by clicking the action button. Method cannot
+   * be used for snack-bar's without action or with custom content.
+   */
+  async dismissWithAction(): Promise<void> {
+    await this._assertSimpleSnackBarWithAction();
+    await (await this._simpleSnackBarActionButton())!.click();
+  }
+
+  /**
+   * Gets the message of the snack-bar. Method cannot be used for
+   * snack-bar's with custom content.
+   */
+  async getMessage(): Promise<string> {
+    await this._assertSimpleSnackBar();
+    return (await this._simpleSnackBarMessage()).text();
+  }
+
+  /**
+   * Asserts that the current snack-bar does not use custom content. Throws if
+   * custom content is used.
+   */
+  private async _assertSimpleSnackBar(): Promise<void> {
+    if (!await this._isSimpleSnackBar()) {
+      throw new Error('Method cannot be used for snack-bar with custom content.');
+    }
+  }
+
+  /**
+   * Asserts that the current snack-bar does not use custom content and has
+   * an action defined. Otherwise an error will be thrown.
+   */
+  private async _assertSimpleSnackBarWithAction(): Promise<void> {
+    await this._assertSimpleSnackBar();
+    if (!await this.hasAction()) {
+      throw new Error('Method cannot be used for standard snack-bar without action.');
+    }
+  }
+
+  /** Gets whether the snack-bar is using the default content template. */
+  private async _isSimpleSnackBar(): Promise<boolean> {
+    return await this._simpleSnackBar() !== null;
+  }
+}