How to test condition function with Jest - Error: Matcher error: received value must be a mock or sp-CodePudding

I start to learning how to do unit test with Jest and I want to test if the modal is open after I click on submit, but I'm getting the error: Matcher error: received value must be a mock or spy function.

 buildform(){
    this.form = this.fb.group({
      firstName: ['',Validators.required],
      secondName:'',
    })
  }
  
  onSubmit(){
    if(this.form.valid){
      this.openModal();
    }
  }

  openModal(){
    ///...
  }

spec.ts

it('should open modal if the form is valid', () => {
    component.buildform();
    component.form.setErrors(null);
    fixture.detectChanges();
    component.onSubmit();

    expect(component.openModal).toHaveBeenCalledWith();
  });

CodePudding user response：

The syntax for testing if a function has been called or not look something like this:

it('should open modal if the form is valid', () => {
  const openModalSpy = jest.spyOn(component, 'openModal');
  component.buildform();
  component.form.setErrors(null);
  fixture.detectChanges();
  component.onSubmit();

  expect(openModalSpy).toHaveBeenCalled();
});

This is because, as the error state, for expect(x).toHaveBeenCalled to work, x have to be a mock like jest.fn() or a spy like jest.spyOn(obj, 'functionName')