Mock on response doesn't work

[bastien-m]

IMPORTANT: Please provide a sample using: http://plnkr.co/edit/lV7zsw7Yqossgs9JOfQU?p=preview

• I'm submitting a ...
  [x ] bug report
  [ ] feature request
  [ ] question about the decisions made in the repository

• What is the current behavior?
  When I try to mock the open function, the real implementation get called during the unit test phase.
  So the code inside the "then(response => {...})" is never reached because there is no response back from the modal.

• If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem via
  https://github.com/bastien-m/ngx-modialog-test

You can reproduce what I'm trying to explain by cloning the repository above.

• What is the expected behavior?
  I expect the unit test to call the mock function instead of the real implementation

• Please tell us about your environment:

Everything is inside the package.json. The project was generated by angular/cli.