javatestingjunitmockingptc-windchill

Creating tests with many mock objects?

I'm having doubts about if I should create tests that have many mock objects or not.

I recently read When should I mock? and I'm feeling confused.

Let's take a look at a method I have (it is just to illustrate the problem)

@Override
protected void validate() throws WTException {
    Either<ImportError, RootFinderResult> rootPart = getDataValidator().getRootPart();
    if (rootPart.isLeft()) {
        addValidationMessage(ROOT_PART_NOT_FOUND);
    } else if (rootPart.isRight()) {
        getObjectsToValidate().forEach(Lambda.uncheckedBiConsumer((part, epmDocuments) -> {
            LocalizableMessage rootRevision = getRevision(part);

            Optional<EPMDocument> wrongRevisionEPM = epmDocuments.stream()
                    .filter(epmDocument -> !isSameRevision(rootRevision, epmDocument))
                    .findAny();

            wrongRevisionEPM.ifPresent(epmDocument -> addValidationMessage("blabla"));
        }));
    }
}

All of the following methods need to have a connection to a server in order to work, otherwise they will throw errors

getDataValidator().getRootPart();
getRevision(part)
!isSameRevision(rootRevision, epmDocument))

In addition I can't create 'real' objects of part or epm documents. This also requires to have a connection to a server.

So at this point, what I really want to test is actually logic of this part of code

    Optional<EPMDocument> wrongRevisionEPM = epmDocuments.stream()
            .filter(epmDocument -> !isSameRevision(rootRevision, epmDocument))
            .findAny();

    wrongRevisionEPM.ifPresent(epmDocument -> addValidationMessage("blabla"));

But to test it I need to mock really many objects 

@Spy
@InjectMocks
private SameRevision sameRevision;
@Mock
private WTPartRelatedObjectDataValidator wTPartRelatedObjectDataValidator;
@Mock
private ValidationEntry validationEntry;
@Mock
private WTPart rootPart1, rootPart2;
@Mock
private EPMDocument epmDocument1, epmDocument2, epmDocument3;
@Mock
private Either<ImportError, RootFinderResult> rootPart;
@Mock
private LocalizableMessage rootPartRevisionOne, rootPartRevisionTwo;

so finally I can test the logic:

@Test
@DisplayName("Should contain error message when part -> epms revisions are not the same")
void shoulHaveErrorMessagesWhenDifferentRevisions() throws Exception {
    doReturn(getMockObjectsToValidate()).when(sameRevision).getObjectsToValidate();

    doReturn(rootPart).when(liebherrWTPartRelatedObjectDataValidator).getRootPart();
    doReturn(false).when(rootPart).isLeft();
    doReturn(true).when(rootPart).isRight();

    doReturn(rootPartRevisionOne).when(sameRevision).getRevision(rootPart1);
    doReturn(rootPartRevisionTwo).when(sameRevision).getRevision(rootPart2);

    doReturn(true).when(sameRevision).isSameRevision(rootPartRevisionOne, epmDocument1);
    doReturn(false).when(sameRevision).isSameRevision(rootPartRevisionOne, epmDocument2);
    doReturn(true).when(sameRevision).isSameRevision(rootPartRevisionTwo, epmDocument3);

    validationEntry = sameRevision.call();

    assertEquals(1, validationEntry.getValidationMessageSet().size());
}

where 

    doReturn(rootPart).when(liebherrWTPartRelatedObjectDataValidator).getRootPart();
    doReturn(false).when(rootPart).isLeft();
    doReturn(true).when(rootPart).isRight();

    doReturn(rootPartRevisionOne).when(sameRevision).getRevision(rootPart1);
    doReturn(rootPartRevisionTwo).when(sameRevision).getRevision(rootPart2);

can be moved to @BeforeEach.

At last, I have my test and it works. It validates what I wanted to be validated but in order to come to this point I had to put a lot of effort to come through the whole API which needs interactions with a server.

What do you guys think, is it worth it to create tests like this? I guess this is a wide-open topic 'cause many newbies that try to come into the 'test world' will have similar a problem, so please do not close the topic because of opinion-based judgement and give your feedback on this topic.

Solution

  • You are right. It is a big effort to mock all those dependencies. Let me get over a few points that may make things clearer: