test(cdk-stepper): preselected value should be number

Author: Abderrahmane Hamila

src/lib/stepper/stepper.spec.ts

@@ -699,13 +699,26 @@ describe('MatStepper', () => {
 
   describe('linear stepper with a pre-defined selectedIndex', () => {
     let preselectedFixture: ComponentFixture<SimplePreselectedMatHorizontalStepperApp>;
+    let stepper: MatHorizontalStepper;
+
     beforeEach(() => {
       preselectedFixture = createComponent(SimplePreselectedMatHorizontalStepperApp);
+      preselectedFixture.detectChanges();
+      stepper = preselectedFixture.debugElement
+          .query(By.directive(MatHorizontalStepper)).componentInstance;
     });
 
     it('should not throw', () => {
       expect(() => preselectedFixture.detectChanges()).not.toThrow();
     });
+
+    it('selectedIndex should be typeof number', () => {
+      expect(typeof stepper.selectedIndex).toBe('number');
+    });
+
+    it('value of selectedIndex should be the pre-defined value', () => {
+      expect(stepper.selectedIndex).toBe(0);
+    });
   });
 
   describe('linear stepper with no `stepControl`', () => {