title: How mock object work in Angular jasmine unit test
body: <p>I am learning unit testing and Angular, so I am beginner in both.
  I have referred several tutorials and articles available on unit testing http in angular.</p>
  
  <p>I am not able to understand that what does httpMock does using HttpTestingController. We call function of actual service then why we call it mock?
  What is underlying process?
  Please refer some article to get better understanding.</p>
  
  <p>Thanks in advance.</p>
  
  <p><strong>Edit:</strong>
  This is the <a href="https://stackoverflow.com/questions/49940214/angular-httpclienttestingmodule-httpmock-giving-error-found-2-requests">issue</a> where I stuck with httpMock.</p>