chore(dropdown): Adding test for active descendant

Author: Ivan Kitanov

projects/igniteui-angular/src/lib/drop-down/drop-down.component.spec.ts

@@ -1046,13 +1046,9 @@ describe('IgxDropDown ', () => {
             beforeEach(() => {
                 fixture = TestBed.createComponent(IgxDropDownTestComponent);
                 fixture.detectChanges();
-                dropdown = fixture.componentInstance.dropDown;
+                dropdown = fixture.componentInstance.dropdown;
             });
             it('should set the aria-label property correctly', () => {
-                fixture = TestBed.createComponent(IgxDropDownTestComponent);
-                fixture.detectChanges();
-                dropdown = fixture.componentInstance.dropdown;
-
                 // Initially aria-label should be null
                 dropdown.toggle();
                 fixture.detectChanges();
@@ -1083,6 +1079,35 @@ describe('IgxDropDown ', () => {
                     expect(item.getAttribute('aria-label')).toBe(`label ${index}`);
                 });
             });
+            it('should update aria-activedescendant to the id of the focused item', fakeAsync(() => {
+                dropdown.toggle();
+                tick();
+                fixture.detectChanges();
+
+                const dropdownElement = fixture.debugElement.query(By.css(`.${CSS_CLASS_DROP_DOWN_BASE}`)).nativeElement;
+                let focusedItem = fixture.debugElement.query(By.css(`.${CSS_CLASS_FOCUSED}`)).nativeElement;
+
+                expect(focusedItem).toBeTruthy();
+                let focusedItemId = focusedItem.getAttribute('id');
+                expect(focusedItemId).toBeTruthy();
+                expect(dropdownElement.getAttribute('aria-activedescendant')).toBe(focusedItemId);
+
+                dropdown.toggle();
+                tick();
+                fixture.detectChanges();
+                dropdown.toggle();
+                tick();
+                fixture.detectChanges();
+
+                UIInteractions.triggerEventHandlerKeyDown('ArrowDown', fixture.debugElement.query(By.css(`.${CSS_CLASS_DROP_DOWN_BASE}`)));
+                tick();
+                fixture.detectChanges();
+
+                focusedItem = fixture.debugElement.query(By.css(`.${CSS_CLASS_FOCUSED}`)).nativeElement;
+                focusedItemId = focusedItem.getAttribute('id');
+
+                expect(dropdownElement.getAttribute('aria-activedescendant')).toBe(focusedItemId);
+            }));
         });
         describe('Grouped items', () => {
             beforeEach(waitForAsync(() => {