How to mock private getters?

Question

I have a class that I want to test. It looks similar to this:

public class ClassUnderTest
{
    private Dependency1 dep1;

    private Dependency1 getDependency1()
    {
       if (dep1 == null)
          dep1 = new Dependency1();
       return dep1;
     }

    public void methodUnderTest()
    {
       .... do something
       getDependency1().InvokeSomething(..);
    }
}

Class Dependency1 is complex and I would like to mock it out when writing a unit test for methodUnderTest().

How do I do that?

@NickJ: I'm not as convinced it is. The advice is going to be generally the same: don't do it, use a different approach to inject those dependencies, etc. — Makoto, May 13 '15 at 15:44

score 2 · Answer 1 · answered May 13 '15 at 14:34

2

I think your architecture needs looking at.

Why not do something like this...

public class MyClass {

  private Dependency dependency;

  public void setDependency(Dependency dep) {
    this.dependency = dep;
  }

  public void myMethod() {
    Result result = dependency.callSomeMethod();
    //do stuff
  }
}

Then in production you could do:

myClass.setDependency(realDependency);

And in test, you could:

myClass.setDependency(mockDependency);

answered May 13 '15 at 14:34

NickJ

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`Dependency` might be very expensive to create, and may never be used. So losing the lazy creation might not be desirable. – David Lavender May 13 '15 at 15:43
In that case, it's easy to instead pass in DependencyFactory – NickJ Jun 02 '15 at 13:17

score 2 · Accepted Answer · answered May 13 '15 at 15:37

It's very easy, and there is no need to mock a private method or change the class under test:

@Test
public void exampleTest(@Mocked final Dependency dep) {
    // Record results for methods called on mocked dependencies, if needed:
    new Expectations() {{ dep.doSomething(); result = 123; }}

    new ClassUnderTest().methodUnderTest();

    // Verify another method was called, if desired:
    new Verifications() {{ dep.doSomethingElse(); }}
}

How to mock private getters?

2 Answers2