test(navDatePicker): fix failing tests, #16356

Author: wnvko

src/material/datepicker/calendar-body.html

@@ -42,7 +42,8 @@
       [style.paddingTop]="_cellPadding"
       [style.paddingBottom]="_cellPadding">
       <button class="mat-calendar-body-cell-content"
-        mat-button
+        mat-button type="button"
+        [attr.aria-label]="item.displayValue"
         [class.mat-calendar-body-selected]="selectedValue === item.value"
         [class.mat-calendar-body-today]="todayValue === item.value">
         {{item.displayValue}}

src/material/datepicker/calendar.spec.ts

@@ -70,15 +70,19 @@ describe('MatCalendar', () => {
 
       let todayCell = calendarElement.querySelector('.mat-calendar-body-today')!;
       expect(todayCell).not.toBeNull();
-      expect(todayCell.innerHTML.trim()).toBe('1');
+      let todayCellSpan = todayCell.querySelector('span')!;
+      expect(todayCellSpan).not.toBeNull();
+      expect(todayCellSpan.innerHTML.trim()).toBe('1');
 
       fakeToday = new Date(2018, 0, 10);
       calendarInstance.updateTodaysDate();
       fixture.detectChanges();
 
       todayCell = calendarElement.querySelector('.mat-calendar-body-today')!;
       expect(todayCell).not.toBeNull();
-      expect(todayCell.innerHTML.trim()).toBe('10');
+      todayCellSpan = todayCell.querySelector('span')!;
+      expect(todayCellSpan).not.toBeNull();
+      expect(todayCellSpan.innerHTML.trim()).toBe('10');
     }));
 
     it('should be in month view with specified month active', () => {