Question

For example , I have a java class as below. I am going to write a unit test for doWork(), so I would like to control obj’s behavior. But it is obvious that obj is instantiated internally.

How can I write this UT? Now I am using Junit+Mockito.

class ToBeTest{
    public ToBeTest(){}
    public boolean doWork(){
        OtherObject obj=new OtherObject();
        return obj.work();
    }
}

Thanks in advance. 🙂

BTW, The reality is I am writing UT for other person’s class. So I don’t want to change it. It has been fully tested by integration test.

Answer 1

If you can’t change the code, you can use Powermock along with junit and Mockito to mock the construction of new objects.

@Test
public void testDoWork() throws Exception{

    MyTest mytest = new MyTest();

    OtherObj obj = new OtherObj();
    obj.test="mocked Test"; //here you can add any other needed values to obj

    PowerMockito.whenNew(OtherObj.class).withNoArguments().thenReturn(obj);

    String result = mytest.doWork();
    Assert.assertTrue(result.equalsIgnoreCase("mocked Test"));
}