test(material/stepper): fixes failing stepper tests

Updates stepper.spec.ts to match updated aria-roles for vertical stepper
so that it is looking for the appropriate roles/attributes.

Author: essjay05

src/material/stepper/stepper.html

@@ -62,9 +62,9 @@
   }
 
   @case ('vertical') {
-    <div class="mat-vertical-stepper-wrapper" role="region">
+    <div class="mat-vertical-stepper-wrapper" role="group">
       @for (step of steps; track step) {
-        <div class="mat-step" role="group">
+        <div class="mat-step">
           <mat-step-header
             class="mat-vertical-stepper-header"
             role="button"
@@ -77,7 +77,7 @@
             [attr.aria-controls]="_getStepContentId($index)"
             [attr.aria-current]="selectedIndex == $index"
             [attr.aria-label]="step.ariaLabel || null"
-            [attr.aria-labelledby]="(!step.ariaLabel && step.ariaLabelledby) ? step.ariaLabelledby : null"
+            [attr.aria-labelledby]="(!step.ariaLabel && step.ariaLabelledby) ? step.ariaLabelledby : _getStepLabelId($index)"
             [attr.aria-disabled]="_stepIsNavigable($index, step) ? null : true"
             [index]="$index"
             [state]="_getIndicatorType($index, step.state)"

src/material/stepper/stepper.spec.ts

@@ -132,11 +132,12 @@ describe('MatStepper', () => {
       expect(stepperComponent.selected instanceof MatStep).toBe(true);
     });
 
-    it('should set the "region" role on the vertical stepper', () => {
-      const stepperEl = fixture.debugElement.query(
-        By.css('mat-vertical-stepper-wrapper'),
-      )!.nativeElement;
-      expect(stepperEl.getAttribute('role')).toBe('region');
+    it('should set the "group" role on a vertical stepper', () => {
+      const stepperWrapper = fixture.debugElement.query(By.css('.mat-vertical-stepper-wrapper'));
+      expect(stepperWrapper).toBeTruthy();
+
+      const stepperEl = stepperWrapper!.nativeElement;
+      expect(stepperEl.getAttribute('role')).toBe('group');
     });
 
     it('should display the correct label', () => {
@@ -383,15 +384,6 @@ describe('MatStepper', () => {
       animationDoneSubscription.unsubscribe();
     });
 
-    it('should set the correct aria-posinset and aria-setsize', () => {
-      const headers = Array.from<HTMLElement>(
-        fixture.nativeElement.querySelectorAll('.mat-step-header'),
-      );
-
-      expect(headers.map(header => header.getAttribute('aria-posinset'))).toEqual(['1', '2', '3']);
-      expect(headers.every(header => header.getAttribute('aria-setsize') === '3')).toBe(true);
-    });
-
     it('should adjust the index when removing a step before the current one', () => {
       const stepperComponent: MatStepper = fixture.debugElement.query(
         By.css('mat-stepper'),