Unit test Subscription angular typescript

Question

I have some class like this

export class Helper {
  static unsubscribeSubscriptions(subscriptions: Subscription[]): void {
    subscriptions.forEach(subscription => {
      if (subscription) {
        subscription.unsubscribe();
      }
    });
  }

  static isNullOrEmpty(value: string): boolean {
    return (!value || value === undefined || value === '' || value.length === 0);
  }
}

I have test one method, but on Subscription i don't even know how to start, this is what I have for now

describe('Helper', () => {
  it('isNullOrEmpty should return true', () => {
    // WHEN
    const value = '';
    const res = Helper.isNullOrEmpty(value);
    // /THEN
    expect(res).toBeTruthy();
  });

  it('isNullOrEmpty should return true', () => {
     // WHEN
     const value = 'FULL';
     const res = Helper.isNullOrEmpty(value);
     // /THEN
     expect(res).toBeFalsy();
  });
});

Does anyone know how to test unsubscribeSubscriptions

Lin Du · Accepted Answer · 2021-08-19 03:07:06Z

Use jasmine.createSpyObj() method to create some mocked subscriptions and pass them to the unsubscribeSubscriptions() method. Assert whether the unsubscribe method on these subscriptions is called.

E.g.

helper.ts:

import { Subscription } from 'rxjs';

export class Helper {
  static unsubscribeSubscriptions(subscriptions: Subscription[]): void {
    subscriptions.forEach((subscription) => {
      if (subscription) {
        subscription.unsubscribe();
      }
    });
  }

  static isNullOrEmpty(value: string): boolean {
    return !value || value === undefined || value === '' || value.length === 0;
  }
}

helper.test.ts:

import { Helper } from './helper';

fdescribe('Helper', () => {
  describe('isNullOrEmpty', () => {
    it('should return true', () => {
      const value = '';
      const res = Helper.isNullOrEmpty(value);
      expect(res).toBeTruthy();
    });

    it('should return false', () => {
      const value = 'FULL';
      const res = Helper.isNullOrEmpty(value);
      expect(res).toBeFalsy();
    });
  });

  describe('unsubscribeSubscriptions', () => {
    it('should unsubscribe all subscriptions', () => {
      const sub1 = jasmine.createSpyObj('sub1', ['unsubscribe']);
      const sub2 = jasmine.createSpyObj('sub1', ['unsubscribe']);
      const subscriptions = [sub1, sub2];
      Helper.unsubscribeSubscriptions(subscriptions);
      expect(sub1.unsubscribe).toHaveBeenCalled();
      expect(sub2.unsubscribe).toHaveBeenCalled();
    });
  });
});

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