CODEWITHSUNDEEP
jasmineangular6karma-jasmine
Abhinav mittal
Abhinav mittal

Reputation: 33

How to unit test this simple function with Angular 6 / Jasmine

I have this below method in one of my components. How can I write a unit test for it?

 getInitialSeats() {
    for (let i = 0; i < 100; i++) {
      i = i + 1;
      this.seatObj = {
        seatName: "Seat- " + i,
        seatId: "seat_" + i
      }
      this.totalSeats.push(this.seatObj);
      this.seatObj = {};
      i = i - 1;
    }
  }

Upvotes: 0

Views: 2166

Answers (1)

Fabian K&#252;ng
Fabian K&#252;ng

Reputation: 6193

Before writing the unit test, I would suggest that you improve your function a bit. There is some code in there that you don't necessarily need. Have a look at this improved function that does the exact same thing.

getInitialSeats() {
  for (let i = 1; i <= 100; i++) {
    this.totalSeats.push({
      seatName: "Seat- " + i,
      seatId: "seat_" + i
    });        
  }
}

To test this function I would just write a very simple test case like this (I assume this function is in a component):

it('should test the initial seats generation', () => {
  // test the before state, i assume the array will be empty beforehand
  expect(component.totalSeats.length).toBe(0);

  // invoke the function
  component.getInitialSeats();

  // test the amount of seats generated
  expect(component.totalSeats.length).toBe(100);

  // test some of the objects generated
  expect(component.totalSeats[0]).toEqual({ seatName: 'Seat-1', seatId: 'seat_1'});
  expect(component.totalSeats[99]).toEqual({ seatName: 'Seat-100', seatId: 'seat_100'});
});

If this function is called somewhere in your component based on an event/interaction then you could set up a spy to check whether it was sucessfully called. A test could look like this:

it('should test the initial seats generation', () => {
  // setup spy and check it hasn't been called yet
  const spy = spyOn(component, 'getInitialSeats').and.callThrough();
  expect(spy).not.toHaveBeenCalled();

  // do something that will invoke the function, here we just call it ourselves
  component.getInitialSeats();

  // check spy
  expect(spy).toHaveBeenCalledTimes(1);

  // test the amount of seats generated
  expect(component.totalSeats.length).toBe(100);

  // test some of the objects generated
  expect(component.totalSeats[0]).toEqual({ seatName: 'Seat-1', seatId: 'seat_1'});
  expect(component.totalSeats[99]).toEqual({ seatName: 'Seat-100', seatId: 'seat_100'});
});

Upvotes: 1

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