使用 Junit 和 Mockito 在方法内创建对象的测试方法

Question

Hello I am fairly new to unit testing with Junit as well as Mockito. I think I have a fairly reasonable understanding of the principles but I can't seem to find any explanations of what I am specifically trying to test online.

I want to test a method, that calls several other methods (void and non-void), which also instantiates objects in the method body. I unfortunately cannot share the code as it is not mine, but here is a general format:

class classToTest {
     private final field_1;

     public void methodToTest( string id, List object_1, List object_2) {
          try {
               Map<SomeObject_1, SomeObject_2> sampleMap = new HashMap<>();
               method_1(object_1, object_2); //void function modifies object_2
               field_1.method_2(id, object_2);
               Map<SomObeject_1, List<object>> groupedList = groupList(object_2)
               //Then some stuff is added to the sampleMap
          }
          //catch would be here
}

At the moment I only care about testing method_1, and I cannot test directly as it is a private method so I must go through this parent method call. I wish I could change the code but I have been asked to keep it the same and to test in this manner with Mockito and Junit.

I know I need to Mock an object of the class to Test as well as its parameter:

private classToTest classToTestObject;
@Mock private field_1 f1;

@Before
public void setup() {
     MockitoAnnotations.init.Mocks(this);
     classToTestObject = mock(classToTest.class, CALLS_REAL_METHODS);
}

but I don't know where to start my actual test, as in how I can essentially just execute that one method call and ignore all the rest. I can't just not ignore the other objects and method calls either as the main method will throw exceptions if they are not handled correctly.

Any help and guidance is much appreciated, sorry that I could not share the code. Thank You!

Answer 1

At the moment I only care about testing method_1, and I cannot test directly as it is a private method so I must go through this parent method call.

Per your comment, and the note in your code:

method_1(object_1, object_2); //void function modifies object_2

You would set up a test that allows you to verify the expected final state of object_2 . You would do this with a real instance of the class, not a mock.

@Test
public void method1Test() {
    // Assemble - your preconditions
    ClassToTest subject = new ClassToTest();
    List<SomeType> object_1 = new ArrayList();
    List<SomeOtherType> object_2 = new ArrayList();

    // Populate object_1 and object_2 with data to use as input
    // that won't throw exceptions. Call any methods on subject that put
    // it in the desired state

    // Act - call the method that calls the method under test
    subject.methodToTest("some id that makes the method run correctly", object_1, object_2);

    // Assert - one or more assertions against the expected final state of object_2
    assertThat(object_2).matchesYourExpectations();
}