Unit testing Angular Jasmine Karma

Question

I'm learning Unit testing and I've

   @Input() showSearchTab: Boolean = false;
     @Input() currentTab: string = null;

     ngOnInit(): void {
        if (this.showSearchTab) {
          this.currentTab = 'search';
        }
      }

This is the unit test:

describe('ngOnInit()', () => { 
        it('should set all the defaults', () => {
          specManager.component.ngOnInit();
          expect(specManager.component.currentTab).toBe('search');
        });
    });

I get an error expected null to be 'search'

Answer 1

As per your logic in ngOnInit function currentTab will have value search if showSearchTab is true .

Thus, before invoking specManager.component.ngOnInit() in your test case, set specManager.component.currentTab = true;

Answer 2

Following your component test, at the moment the test hits the expectation, showSearchTab is set to false, so it doesn't pass the if condition. To have a fully tested scenario, you should do:

describe('ngOnInit()', () => {
    describe('and showSearchTab is set to false', () => {
        it('should set all the defaults', () => {
            specManager.component.showSearchTab = false;
            specManager.component.ngOnInit();
            expect(specManager.component.currentTab).toBeNull();
        });
    });

    describe('and showSearchTab is set to true', () => {
        it('should set all the defaults', () => {
            specManager.component.showSearchTab = true;
            specManager.component.ngOnInit();
            expect(specManager.component.currentTab).toEqual('search');
        });
    });
});