Part of the class called from the class under test in JMockit Mock method memo

Required situation

If you want to Mock only some methods of the class called from the class under test

JMockit 1.46

Conclusion

1. Pass the instance you want to Mock to Expectations and define only the method you want to Mock in Expectations
2. Set (forcibly) to the test target class

Tested class

public class Sample {

	@Inject
	Hoge hoge;

	public String getHoge() {
		return hoge.getHoge() + hoge.getHogeUpper();
	}
}

I'm using Hoge's method injected from the class under test. This is a workaround if you want to partially mock the Hoge.

Class called from the class under test

public class Hoge {

	public String getHoge() {
		return "hoge";
	}

	public String getHogeUpper() {
		return null;
	}
}

Please assume that getHoge has been implemented and getHogeUpper has not been implemented yet.

Test failed

public class SampleTest {

	@Tested
	Sample sample;

 	@Injectable
	Hoge hoge;

	/**
	 *A case where you want to Mock only some methods of the class called from the class under test.
	 *The test fails.
	 */
	@Test
	public void test() {

		new Expectations(hoge) {{
			hoge.getHogeUpper();
			result = "HOGE";
		}};

		String actual = sample.getHoge();
		assertThat(actual, is("hogeHOGE")); //actual becomes null HOGE
	}
}

Since the class under test uses Inject, I would normally like to inject instances with @Tested and @Injectable in JMockit, but that would cause the test to fail. The reason is that @Injectable will empty all Hoge methods.

Test successful

public class SampleTest2 {

	Sample sample = new Sample();

	/**
	 *A case where you want to Mock only some methods of the class called from the class under test.
	 *The test succeeds.
	 * @throws Exception
	 * @throws NoSuchFieldException
	 */
	@Test
	public void test() throws NoSuchFieldException, Exception {

		Hoge hoge = new Hoge();
		new Expectations(hoge) {
			{
				hoge.getHogeUpper();
				result = "HOGE";
			}
		};

		//Set a partially Mocked hoge in the private field of Sample
        Field field = sample.getClass().getDeclaredField("hoge");
        field.setAccessible(true);
        field.set(sample, hoge);

		String actual = sample.getHoge();
		assertThat(actual, is("hogeHOGE"));
	}
}

See below for more information on partial Mock. https://jmockit-ja.nyamikan.net/tutorial/Mocking.html#partial The test is successful by setting the partially Mocked Mock instance to the test target class by reflection.

Finally

In older versions of JMockit, only part of it was Mocked with MockUp , and the instance obtained with getMockInstance was set in the test class with Deencapsulation.setField, but in 1.46 both methods disappeared. .. .. Please be careful when updating the version of JMockit, as the API is frequently deleted. Please let me know if there is any other good way.