How to mock private method of an abstract class

Question

public abstract class ClassA extends {

        public String getName(){
          String lastName = getLastName();
          return "Language"+lastName;
        }

        private String getLastName(){
          return "Java";
        }
}

I am writing the test for getName. I want to mock getLastName method. How can i do it?

Answer 1

You can try approach from that answer.

However, if logic in private method is complex and class needs separate testing for it, it's a sure sign that you need some refactoring.

According to SOLID principles your private method should be public, and also should be placed in derived class.

public abstract class ClassA {
  private final LastNameProvider provider;

  public ClassA(LastNameProvider provider) {
    this.provider = provider;
  }

  public String getName() {
    String lastName = provider.getLastName();
    return "Language"+lastName;
  }
}

public interface LastNameProvider {
  String getLastName()
}

public class JavaLastNameProvider {
  private String getLastName(){
    return "Java";
  }
}

With that approach you can easily replace provider in ClassA with another one for testing, or you can mock it with Mockito and so on.