feat(cdk/testing): add loaderForDocumentRoot method to `TestbedHarn…

…essEnvironment`

This should have been included as part of angular#16709, but got overlooked
somehow

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> {
-  constructor(rawRootElement: Element, private _fixture: ComponentFixture<unknown>) {
+  protected constructor(rawRootElement: Element, private _fixture: ComponentFixture<unknown>) {
     super(rawRootElement);
   }
 
@@ -23,6 +23,11 @@ export class TestbedHarnessEnvironment extends HarnessEnvironment<Element> {
     return new TestbedHarnessEnvironment(fixture.nativeElement, fixture);
   }
 
+  /** Creates a `HarnessLoader` rooted at the document root element. */
+  static loaderForDocumentRoot(fixture: ComponentFixture<unknown>): HarnessLoader {
+    return new TestbedHarnessEnvironment(document.body, fixture);
+  }
+
   /**
    * Creates an instance of the given harness type, using the fixture's root element as the
    * harness's host element. This method should be used when creating a harness for the root element

src/material-experimental/mdc-dialog/harness/dialog-harness-filters.ts

@@ -6,6 +6,6 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
- import {BaseHarnessFilters} from '@angular/cdk-experimental/testing';
+import {BaseHarnessFilters} from '@angular/cdk-experimental/testing';
 
 export interface DialogHarnessFilters extends BaseHarnessFilters {}

src/material-experimental/mdc-dialog/harness/dialog-harness.spec.ts

@@ -22,7 +22,7 @@ describe('MatDialogHarness', () => {
 
       fixture = TestBed.createComponent(DialogHarnessTest);
       fixture.detectChanges();
-      loader = new TestbedHarnessEnvironment(document.body, fixture);
+      loader = TestbedHarnessEnvironment.loaderForDocumentRoot(fixture);
       dialogHarness = MatDialogHarness;
     });