feat(material-experimental/mdc-snack-bar): add test harness (#20366)

Adds a test harness for the MDC-based snack bar. One gotcha here compared to the standard snack bar is that the harness excludes (via a CSS selector) instances that are in the process of being closed. We have to take this approach, because MDC's animations are run outside of Angular and we don't have a way of waiting for them to finish.

src/material-experimental/config.bzl

@@ -34,6 +34,7 @@ entryPoints = [
     "mdc-slider",
     "mdc-slider/testing",
     "mdc-snack-bar",
+    "mdc-snack-bar/testing",
     "mdc-table",
     "mdc-table/testing",
     "mdc-tabs",

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

@@ -0,0 +1,41 @@
+load("//tools:defaults.bzl", "ng_test_library", "ng_web_test_suite", "ts_library")
+
+package(default_visibility = ["//visibility:public"])
+
+ts_library(
+    name = "testing",
+    srcs = glob(
+        ["**/*.ts"],
+        exclude = ["**/*.spec.ts"],
+    ),
+    module_name = "@angular/material-experimental/mdc-snack-bar/testing",
+    deps = [
+        "//src/cdk/testing",
+    ],
+)
+
+filegroup(
+    name = "source-files",
+    srcs = glob(["**/*.ts"]),
+)
+
+ng_test_library(
+    name = "unit_tests_lib",
+    srcs = glob(["**/*.spec.ts"]),
+    deps = [
+        ":testing",
+        "//src/material-experimental/mdc-snack-bar",
+        "//src/material/snack-bar/testing:harness_tests_lib",
+    ],
+)
+
+ng_web_test_suite(
+    name = "unit_tests",
+    static_files = [
+        "@npm//:node_modules/@material/snackbar/dist/mdc.snackbar.js",
+    ],
+    deps = [
+        ":unit_tests_lib",
+        "//src/material-experimental:mdc_require_config.js",
+    ],
+)

src/material-experimental/mdc-snack-bar/testing/index.ts

@@ -0,0 +1,9 @@
+/**
+ * @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
+ */
+
+export * from './public-api';

src/material-experimental/mdc-snack-bar/testing/public-api.ts

@@ -0,0 +1,10 @@
+/**
+ * @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
+ */
+
+export * from './snack-bar-harness';
+export * from './snack-bar-harness-filters';

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

@@ -0,0 +1,12 @@
+/**
+ * @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 {BaseHarnessFilters} from '@angular/cdk/testing';
+
+/** A set of criteria that can be used to filter a list of `MatSnackBarHarness` instances. */
+export interface SnackBarHarnessFilters extends BaseHarnessFilters {}

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

@@ -0,0 +1,7 @@
+import {MatSnackBarModule, MatSnackBar} from '@angular/material-experimental/mdc-snack-bar';
+import {runHarnessTests} from '@angular/material/snack-bar/testing/shared.spec';
+import {MatSnackBarHarness} from './snack-bar-harness';
+
+describe('MDC-based MatSnackBarHarness', () => {
+  runHarnessTests(MatSnackBarModule, MatSnackBar, MatSnackBarHarness as any);
+});

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

@@ -0,0 +1,122 @@
+/**
+ * @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, HarnessPredicate} from '@angular/cdk/testing';
+import {SnackBarHarnessFilters} from './snack-bar-harness-filters';
+
+/** Harness for interacting with an MDC-based mat-snack-bar in tests. */
+export class MatSnackBarHarness extends ComponentHarness {
+  // Developers can provide a custom component or template for the
+  // snackbar. The canonical snack-bar parent is the "MatSnackBarContainer".
+  // We use `:not([mat-exit])` to exclude snack bars that are in the process of being dismissed,
+  // because the element only gets removed after the animation is finished and since it runs
+  // outside of Angular, we don't have a way of being notified when it's done.
+  /** The selector for the host element of a `MatSnackBar` instance. */
+  static hostSelector = '.mat-mdc-snack-bar-container:not([mat-exit])';
+
+  private _simpleSnackBar = this.locatorForOptional('.mat-mdc-simple-snack-bar');
+  private _simpleSnackBarMessage =
+      this.locatorFor('.mat-mdc-simple-snack-bar .mat-mdc-snack-bar-label');
+  private _simpleSnackBarActionButton =
+      this.locatorForOptional('.mat-mdc-simple-snack-bar .mat-mdc-snack-bar-action');
+
+  /**
+   * Gets a `HarnessPredicate` that can be used to search for a `MatSnackBarHarness` that meets
+   * certain criteria.
+   * @param options Options for filtering which snack bar instances are considered a match.
+   * @return a `HarnessPredicate` configured with the given options.
+   */
+  static with(options: SnackBarHarnessFilters = {}): HarnessPredicate<MatSnackBarHarness> {
+    return new HarnessPredicate(MatSnackBarHarness, options);
+  }
+
+  /**
+   * 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>;
+  }
+
+  /**
+   * 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();
+  }
+
+  /** Gets whether the snack-bar has been dismissed. */
+  async isDismissed(): Promise<boolean> {
+    // We consider the snackbar dismissed if it's not in the DOM. We can assert that the
+    // element isn't in the DOM by seeing that its width and height are zero.
+
+    const host = await this.host();
+    const [exit, dimensions] = await Promise.all([
+      // The snackbar container is marked with the "exit" attribute after it has been dismissed
+      // but before the animation has finished (after which it's removed from the DOM).
+      host.getAttribute('mat-exit'),
+      host.getDimensions(),
+    ]);
+
+    return exit != null || (!!dimensions && dimensions.height === 0 && dimensions.width === 0);
+  }
+
+  /**
+   * Asserts that the current snack-bar does not use custom content. Promise rejects if
+   * custom content is used.
+   */
+  private async _assertSimpleSnackBar(): Promise<void> {
+    if (!await this._isSimpleSnackBar()) {
+      throw 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 the promise will reject.
+   */
+  private async _assertSimpleSnackBarWithAction(): Promise<void> {
+    await this._assertSimpleSnackBar();
+    if (!await this.hasAction()) {
+      throw Error('Method cannot be used for standard snack-bar without action.');
+    }
+  }
+
+  /** Whether the snack-bar is using the default content template. */
+  private async _isSimpleSnackBar(): Promise<boolean> {
+    return await this._simpleSnackBar() !== null;
+  }
+}

src/material/snack-bar/testing/shared.spec.ts

@@ -1,7 +1,7 @@
 import {OverlayContainer} from '@angular/cdk/overlay';
 import {HarnessLoader} from '@angular/cdk/testing';
 import {TestbedHarnessEnvironment} from '@angular/cdk/testing/testbed';
-import {Component, TemplateRef, ViewChild} from '@angular/core';
+import {Component, TemplateRef, ViewChild, Injector} from '@angular/core';
 import {ComponentFixture, inject, TestBed} from '@angular/core/testing';
 import {MatSnackBar, MatSnackBarConfig, MatSnackBarModule} from '@angular/material/snack-bar';
 import {NoopAnimationsModule} from '@angular/platform-browser/animations';
@@ -13,6 +13,7 @@ import {MatSnackBarHarness} from './snack-bar-harness';
  */
 export function runHarnessTests(
     snackBarModule: typeof MatSnackBarModule,
+    snackBarToken: typeof MatSnackBar,
     snackBarHarness: typeof MatSnackBarHarness) {
   let fixture: ComponentFixture<SnackbarHarnessTest>;
   let loader: HarnessLoader;
@@ -140,25 +141,24 @@ export function runHarnessTests(
     snackBar = await loader.getHarness(snackBarHarness);
     await expectAsync(snackBar.dismissWithAction()).toBeRejectedWithError(/without action/);
   });
-}
 
-@Component({
-  template: `
-      <ng-template>
-          My custom snack-bar.
-      </ng-template>
-  `
-})
-class SnackbarHarnessTest {
-  @ViewChild(TemplateRef) customTmpl: TemplateRef<any>;
+  @Component({
+    template: `<ng-template>My custom snack-bar.</ng-template>`
+  })
+  class SnackbarHarnessTest {
+    @ViewChild(TemplateRef) customTmpl: TemplateRef<any>;
+    snackBar: MatSnackBar;
 
-  constructor(readonly snackBar: MatSnackBar) {}
+    constructor(injector: Injector) {
+      this.snackBar = injector.get(snackBarToken);
+    }
 
-  openSimple(message: string, action = '', config?: MatSnackBarConfig) {
-    return this.snackBar.open(message, action, config);
-  }
+    openSimple(message: string, action = '', config?: MatSnackBarConfig) {
+      return this.snackBar.open(message, action, config);
+    }
 
-  openCustom(config?: MatSnackBarConfig) {
-    return this.snackBar.openFromTemplate(this.customTmpl, config);
+    openCustom(config?: MatSnackBarConfig) {
+      return this.snackBar.openFromTemplate(this.customTmpl, config);
+    }
   }
 }

src/material/snack-bar/testing/snack-bar-harness.spec.ts

@@ -1,7 +1,7 @@
-import {MatSnackBarModule} from '@angular/material/snack-bar';
+import {MatSnackBarModule, MatSnackBar} from '@angular/material/snack-bar';
 import {runHarnessTests} from '@angular/material/snack-bar/testing/shared.spec';
 import {MatSnackBarHarness} from './snack-bar-harness';
 
 describe('Non-MDC-based MatSnackBarHarness', () => {
-  runHarnessTests(MatSnackBarModule, MatSnackBarHarness);
+  runHarnessTests(MatSnackBarModule, MatSnackBar, MatSnackBarHarness);
 });