fix(material/slide-toggle): account for disabledInteractive in harness

Switches to using a CSS class to get the disabled state in the harness so it continues to work when `disabledInteractive` is set.

(cherry picked from commit c3e0279)

Author: crisbeto

src/material/slide-toggle/slide-toggle.html

@@ -17,7 +17,7 @@
     [attr.aria-describedby]="ariaDescribedby"
     [attr.aria-required]="required || null"
     [attr.aria-checked]="checked"
-    [attr.aria-disabled]="disabledInteractive && disabledInteractive ? 'true' : null"
+    [attr.aria-disabled]="disabled && disabledInteractive ? 'true' : null"
     (click)="_handleClick()"
     #switch>
     <span class="mdc-switch__track"></span>

src/material/slide-toggle/testing/slide-toggle-harness.spec.ts

@@ -160,6 +160,17 @@ describe('MatSlideToggleHarness', () => {
     await disabledToggle.toggle();
     expect(await disabledToggle.isChecked()).toBe(false);
   });
+
+  it('should get disabled state when disabledInteractive is enabled', async () => {
+    fixture.componentInstance.disabled.set(false);
+    fixture.componentInstance.disabledInteractive.set(true);
+
+    const toggle = await loader.getHarness(MatSlideToggleHarness.with({label: 'Second'}));
+    expect(await toggle.isDisabled()).toBe(false);
+
+    fixture.componentInstance.disabled.set(true);
+    expect(await toggle.isDisabled()).toBe(true);
+  });
 });
 
 @Component({
@@ -171,7 +182,10 @@ describe('MatSlideToggleHarness', () => {
           aria-label="First slide-toggle">
         First
       </mat-slide-toggle>
-      <mat-slide-toggle [disabled]="disabled()" aria-labelledby="second-label">
+      <mat-slide-toggle
+        [disabled]="disabled()"
+        [disabledInteractive]="disabledInteractive()"
+        aria-labelledby="second-label">
         Second
       </mat-slide-toggle>
       <span id="second-label">Second slide-toggle</span>
@@ -182,4 +196,5 @@ describe('MatSlideToggleHarness', () => {
 class SlideToggleHarnessTest {
   ctrl = new FormControl(true);
   disabled = signal(true);
+  disabledInteractive = signal(false);
 }

src/material/slide-toggle/testing/slide-toggle-harness.ts

@@ -70,8 +70,14 @@ export class MatSlideToggleHarness extends ComponentHarness {
 
   /** Whether the slide-toggle is disabled. */
   async isDisabled(): Promise<boolean> {
-    const disabled = (await this._nativeElement()).getAttribute('disabled');
-    return coerceBooleanProperty(await disabled);
+    const nativeElement = await this._nativeElement();
+    const disabled = await nativeElement.getAttribute('disabled');
+
+    if (disabled !== null) {
+      return coerceBooleanProperty(disabled);
+    }
+
+    return (await nativeElement.getAttribute('aria-disabled')) === 'true';
   }
 
   /** Whether the slide-toggle is required. */