change-detection.spec.ts

describe('change detection', () => {

    let failure = 'There should be the exception: Expression has changed after it was checked';
    let spy: any;
    let myIt: any;
    beforeEach(() => {
      fixture.autoDetectChanges(true);

      patchChangeDetection();

      let errHandler = (err: any) => {
        myIt.result.failedExpectations = [];  // clear the failed expectations. fail again ...
        if (err.error.message.indexOf('Expression has changed after it was checked') === -1) {
          fail(failure);
        }
      };
      spy = jasmine.createSpy('errHandler', errHandler).and.callThrough();
    });

    myIt = it(`throws a "change detection error" if the fruit price > 100
               and and the user does not provide a budget value`, () => {

      fillValue('#budget', 100);
      fillValue('#fruit0', 100); // apples

      fixture.ngZone.onError.subscribe(spy);

      clearBudgetAndLeave();

      expect(spy.calls.count()).toBe(1, failure);  // error occurred => spec passed
    });

  });