Angular + Jasmine: How to ignore/ mock one function in the tested component (not in a dependency)?

user_14835689 0
Viewed 1476

I know how to mock a function from a dependency, but now I have one function that is not in a dependency, it's in the actual component that I want to test. How can I tell jasmine to simply ignore it?

When I run ng test this test fails:

enter image description here

The reason for this is this function that I import from an external library:

import { documentToHtmlString } from '@contentful/rich-text-html-renderer';

(Contentful is a content managament service that I use in my project.)

In my component this function gets called here:

ngOnInit() {
  
  //the next line keeps the test from creating, I don't really care to test this function, how can I mock it?:
  this.serializeContentfulRichText(someContentfulTextDoesntMatter);
  
  // a lot more stuff that I actually need to test
  ...
}

serializeContentfulRichText(contentfulText: any) {
    return documentToHtmlString(contentfulText, this.myRenderingOptions);
}

When I delete the documentToHtmlString line and just return null the rest of the test works and I can test my whole component. But of course I can't just delete this line in my actual component, I just want to ignore/mock it in my test.

I tried it with a spy:

it('should create', () => {
    let spy = spyOn(component, 'serializeContentfulRichText')
    expect(spy).toHaveBeenCalledTimes(1)
    expect(component).toBeTruthy();
  });

But the spy doesn't get called and the component doesnt get created (Both expectations fail).

jasmine contentful angular mocking unit-testing
1 Answers

If you want to stub a method of a testing component, you need to do it after TestBed.createComponent, but before fixture.detectChanges().

In this case, only constructor of the component has been executed, but not lifecycle hooks.

it('should create', () => {
  // initialization
  const fixture = TestBed.createComponent(DeclarationScrolltextComponent);
  const component = fixture.componentInstance;
  expect(component).toBeTruthy();

  // installing spies
  const spy = spyOn(component, 'serializeContentfulRichText');
  
  // executing render
  fixture.detectChanges();

  // assertions
  expect(spy).toHaveBeenCalledTimes(1);
});
user_131120180
Related