[FIXED] When should I mock or not mock external/dependent public interface

Issue

I am trying to write unit test for the following class

I was wondering if I need to mock the Dependency class (consider that it is purely logic no DB or external rest calls are made).

I was thinking if I will not mock the Dependency class, then anyway it will be covered by the CUT or should I mock it and write separate unit test suite for Dependency class public interface.

public class ClassUnderTest {
  @Autowired
  private Dependency dependency;

  public Object foo(){
    // do something
    var = dependeny.bar(args..);
    // do somethig
  }
}

public class Dependency {
  public Object bar(args..){
    // do something
  }
}

Solution

The main idea of unit testing is to test units separately. Otherwise, it would be an integration test.

In this case, you need to write a separate test suite for Dependency, and mock the call to it in ClassUnderTest.

Answered By - amseager