How to mock DynamoDB with Mockito?

Question

I got some code which already makes my DynamoDB instance mocked using PowerMockito like that:

@Mock
private DynamoDB dynamoDB;
 .....
PowerMockito.whenNew(DynamoDB.class).withAnyArguments().thenReturn(dynamoDB);

Our code coverage plugin doesn't like PowerMockito so he doesn't include these tests in the code coverage.

Due to that, now I need to use Mockito instead of PowerMockito.

I tried the following code below to make my DynamoDB mocked, but it failed:

DynamoDB mockedInstance = Mockito.mock(DynamoDB.class);
Mockito.doReturn(mockedInstance).when(carFactorySpy).carFactoryMethod("us-west-2");

The DynamoDB is being created like:

DynamoDB ddbCon = new DynamoDB(Regions.fromName(region));

or -

DynamoDB ddbCon = new DynamoDB(Regions.US_WEST_2);

Answer 1

Use Mockito.initMocks() or MockitoJUnitRunner annotation to setup mocking for your test. Also, it would be nice to provide with the failure message you are getting.

Answer 2

The details of your implementation are still a little unclear to me but here's a try.

If your test subject looks like...

private CarFactory carFactory;

public void foo() {
    DynamoDB ddbCon = carFactory.carFactoryMethod("us-west-2"));
    // use ddbCon
}

Then your unit test could look something like...

@Mock
private CarFactory carFactory;

@Test
public void fooShouldUseMockDynamoDb() {
    DynamoDb ddbCon = mock(DynamoDB.class);
    when(carFactory.carFactoryMethod("us-west-2")).thenReturn(ddbCon);
    // stub ddbCon
}

FWIW, I also try to avoid PowerMockito but more so because it is slow then code coverage not being captured.