describe('Some test description', () => {
  let _reject;

  beforeEach(() => {
    _reject = Promise.reject()
    _reject.catch(() => { })

    /* More implementation... */
  })

  it('Test with error', () => {
    const someMockError = jasmine.createSpy().and.returnValue(
      Promise.reject(new Error('Unit Test Error'))
    )

    /* The rest of implementation using this mock... */
  })
})