模拟测试void方法，重写成员变量

Question

I'm new to unit-testing and mockito but i need to test this class:

public class XMLHandler {
    private static final String CONFIG_FILE = "path/to/xml";
    private XMLConfiguration config = null;

    public XMLHandler() {
        try {
            config = new XMLConfiguration(CONFIG_FILE);
            config.setValidating(true);
        } catch (ConfigurationException e) {
            LOGGER.log(Level.SEVERE, e );
        }
    }

    public List<ConfigENtries> getEntries() {     
        // do some stuff
        return list;
    }

    @Override
    public void removeEntry(int index) {
        // remove entry
    }
}

I think i have to override the config variable with a mockup but i don't have a setter, so how would i do this? And what about removeEntry? How to test a void method?

I hope someone can help me with this

Answer 1

As you are allowed to modify your class, I would suggest the following structure:

public class XMLHandler {
  private final XMLConfiguration config;

  public XMLHandler(XMLConfiguration config) {
    this.config = config;
  }

  public List<ConfigENtries> getEntries() {     
    // do some stuff
    return list;
  }

  @Override
  public void removeEntry(int index) {
    // remove entry
  }
}

Make sure that XMLConfiguration is an interface , not a concrete implementation. Then you can mock the config parameter passed to your constructor. ( Note: you can mock non-final concrete class too, but using an interface would be preferred .)

You can then test the public methods of XMLHandler and confirm correct behaviour by inspecting the calls made to config and asserting the method responses are correct.

Void methods can be tested without problem. You just need some way of determining that the state of your object and the world has been adjusted corrected. So, perhaps you need to call a getter method at the end of your test to ensure values have changed. Or verify expected calls were made to your mock object.

Answer 2

Although I would also prefer modifying the constructor and pass XMLConfiguration like @DuncanJones suggests (or use some other kind of Dependency Injection), you could use mockito to mock XMLConfiguration by using the @InjectMocks annotation in your test:

@RunWith(MockitoJUnitRunner.class)
public class XMLHandlerTest {

    @InjectMocks
    XMLHandler handler = new XMLHandler();

    @Mock
    XMLConfiguration config;

    //...