Evaluating a branch using Jasmine Karma

How can I effectively test a branch using Jasmin/Karma within Angular? Consider the following simple function:

loadData(){
    if(this.faktor){ // here it should be true or false
      this.callMethod1();
    }else{
      this.callMethod2();
    }
}

I am looking to increase the test coverage and need to test the branches. I attempted the following example but encountered issues. How can I set this.factor.isExist() to true?

Below is my test component code:

import { async, ComponentFixture, TestBed } from '@angular/core/testing';

import { ChartComponent } from './chart.component';

describe('ChartComponent', () => {
  let component: ChartComponent;
  let fixture: ComponentFixture<ChartComponent>;

  beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations: [ ChartComponent ]
    })
    .compileComponents();
  }));

  beforeEach(() => {
    fixture = TestBed.createComponent(ChartComponent);
    component = fixture.componentInstance;
    fixture.detectChanges();
  });

  it('should create', () => {
    expect(component).toBeTruthy();
  });

  it('should call method1 if factor exists', () => {
    const spy = spyOn(component, 'callMethod1');
    component.factor.isExist() as true;
    expect(spy).toHaveBeenCalled();
  })

  it('should call method2 if factor does not exist', () =>{
    const spy = spyOn(component, 'callMethod2');
    component.factor.isExist() as false;
    expect(spy).toHaveBeenCalled();
  })
});

Answer №1

While achieving 100% code coverage may not always be possible, in this specific scenario it is quite achievable to cover all the code being presented.

it('should trigger method1 if factor is present', () => {
    const spy = spyOn(component, 'callMethod1');
    component.factor = 'Your mock data goes here'
    component.loadData();       // should execute if part
    expect(spy).toHaveBeenCalled();
})

it('should trigger method2 if factor is not present', () =>{
    const spy =  spyOn(component, 'callMethod2');
    component.factor = null;    
    component.loadData();     // should execute else part
    expect(spy).toHaveBeenCalled();
})

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