How can I test that a function was called inside an if statement in jasmine-karma

Question

I'm creating an Angular app and I'm learning unit test and I want to test certain method, but I can't manage to test that the function enters in the if statement. I don't know how to force it. Could you please teach me how to do that? This is the function:

currentRoute(): void {
    const router: Router = this.injector.get(Router);
    router.events.subscribe((val) => {
        if (val instanceof NavigationEnd) {
             this.checkMenuLinks(val);
        }
    });
}

If I run a test-coverage I get al the if statement in red, as not tested. Could you please tell me how to achieve this? Thank you so much.

Answer 1

Most likely you're not triggering router events in your unit test - which is quite normal

You should look up the Angular RouterTestingModule

• https://angular.io/api/router/testing/RouterTestingModule

There's some good tutorials on testing the routes themselves, and you'll be looking to trigger the Navigation End event, which should occur during the process. You can add a jasmine spy to the checkMenuLinks() method to check if it's been called

• https://dev.to/this-is-angular/testing-angular-routing-components-with-the-routertestingmodule-4cj0

Other approaches involved mocking the Router service, and often this is the most efficient approach