Jasmine spy on base class protected property

Question

I have a scenario to spy the protected property from the base class.

export class BaseClass {
    protected property1: string;
}

export class InheritedClass extends BaseClass, OnInit {

   ngOnInit() {
        this.populateProperties();
   }

   populateProperties() {
       this.property1 = "test";
   } 
}

I am trying to write the unit test for this but is returning property1 not found. What could be the issue?

describe('populateProperties', () => {
    it('should assign the properties values', () => {
      // arrange
      const spy = spyOnProperty((component as any), 'property1');

      // act
      component.populateProperties();

      // assert
      expect(spy).toBeDefined();

    });
  });

score 1 · Accepted Answer · answered May 22 '20 at 13:08

It's an instance variable, not a function so therefore it cannot be spied upon.

Try this:

describe('populateProperties', () => {
    it('should assign the properties values', () => {
      // act
      component.populateProperties();

      // assert
      expect((component as any).property1).toBeDefined();
    });
  });

I assume the any is required because property1 is protected in the BaseClass but this is not best practice. You should only be testing the HTML/View, public methods, and public properties of your component.

Jasmine spy on base class protected property

1 Answers1