Spring boot Mockito mocking method from imported class

Question

I'm fairly new to Mockito and I have been developing many test cases lately, like a lot. I now have a better understanding of mocking and stubbing.

But now I have this problem, which I'm sure I can't find the answer because of the words I'm using, and the results it gives because of the word "import", still I have tried hard to find a solution to my problem without luck, so I'm going to ask.

I have this class, which uses import, like all classes, but one method is being using directly from the imports.

Having the following class:

package package;

import another.package.OutsideUtils;

@Service
public class ClassBeingTested implements anotherClass {

  @Override
  public void MethodBeingTested () {
    if(OutsideUtils.getBoolean()) {
      //do stuff
    }
  }
}

And in my test class

package testpackage;

@ExtendWith(MockingExtension.class)
class ClassBeingTestedTest {

  @InjectMocks
  ClassBeingTested classBeingTested;
  
  @Test
  void whenMethodBeingTeste_ReturnTrue() {
  
   when(OutsideUtils.getBoolean()).thenReturn(true);
   
   classBeingTested.MethodBeingTested();
   
  }
  
  @Test
  void whenMethodBeingTeste_ReturnFalse() {
  
   when(OutsideUtils.getBoolean()).thenReturn(false);
   
   classBeingTested.MethodBeingTested();
   
  }
}

This is just to exemplify what I need, I want to know if it is possible to do the when(OutsideUtils.getBoolean()).thenReturn(true) (or return false), and if not, what's the way to achieve this doing a minimun refactor in my class being tested.

Also using only mockito, no powermockito please.

Answer 1

Yes it is, here it is how:

In that case you are testing trying to use the when() method with a static method from that OutsideUtils, it won't work because the when() method requires a method from a mock.

Here is a valid usage of that when() method.

@ExtendWith(MockitoExtension.class)
public class ItemServiceTest {

    @InjectMocks
    private ItemService itemServiceMock;

    @Mock
    private ItemRepository itemRepositoryMock;

    @Test
    public void fetchItems_basic() {
        // arrange
        List<Item> items = Arrays.asList(new Item(1, "first", 10, 100), new Item(2, "second", 20, 200));
        Integer expectedResultFirst = 1000;
        Integer expectedResultSecond = 4000;
        when(itemRepositoryMock.findAll()).thenReturn(items);

        // act
        List<Item> actualResult = itemServiceMock.fetchItems();

        // assert
        assertEquals(expectedResultFirst, actualResult.get(0).getValue());
        assertEquals(expectedResultSecond, actualResult.get(1).getValue());

   }
}

The solution for your example.

Since the latest versions of mockito you can mock static methods. You just need to add a dependency to your pom.xml.

<dependency>
  <groupId>org.mockito</groupId>
  <artifactId>mockito-inline</artifactId>
  <version>3.8.0</version>
  <scope>test</scope>
</dependency>

You will have to use mockStatic() method to create a MockedStatic, and use the when() method from the MockedStatic class, and then the logic is basically the same as any other usage of unit tests.

@ExtendWith(MockitoExtension.class)
class ClassBeingTestedTest {

  @InjectMocks
  private ClassBeingTested classBeingTested;

  @Test
  void whenMethodBeingTeste_ReturnTrue() {
      // arrange
      MockedStatic<OutsideUtils> utilities = Mockito.mockStatic(OutsideUtils.class);
      utilities.when(OutsideUtils::getBoolean).thenReturn(true);

      // act
      Boolean result = classBeingTested.methodBeingTested();

      // assert
      assertEquals(true, result);
  }

  @Test
  void whenMethodBeingTeste_ReturnFalse() {
      // arrange
      MockedStatic<OutsideUtils> utilities = Mockito.mockStatic(OutsideUtils.class);
      utilities.when(OutsideUtils::getBoolean).thenReturn(false);

      // act
      Boolean result = classBeingTested.methodBeingTested();

      // assert
      assertEquals(false, result);
  }
}