Random crash with OCMock

Question

Sometimes I get a EXC_BAD_ACCESS when running this test:

- (void)testThatItDoesNotSaveLoadedImageIfNotIntializedWithModifiesFileCacheOption {

    id cacheMock = OCMClassMock([BEImageCache class]);
    id imageLoaderMock = OCMClassMock([BEImageLoader class]);

    BETwoLayerCacheImageProvider *imageProvider = [[BETwoLayerCacheImageProvider alloc] initWithCache:cacheMock imageLoader:imageLoaderMock options:0 scale:2.f];
    UIImage *expectedImage = [UIImage new];
    [[cacheMock reject] saveImageAtURLInFileCache:[OCMArg any] forURL:[OCMArg any]];
    [[cacheMock reject] saveImageInFileCache:[OCMArg any] forURL:[OCMArg any]];

    __block NSURL *URL = [NSURL fileURLWithPath:@"/file:///fixtureURL"];
    __block typeof(self) welf = self;
    OCMStub([imageLoaderMock downloadImageWithURL:[OCMArg any] completionCallback:[OCMArg any]]).andDo(^(NSInvocation *invocation) {

        ///[invocation retainArguments];
        void (^callback)(UIImage *image, NSError *error, NSString *imageURL, NSURL *temporaryImageURL) = nil;
        [invocation getArgument:&callback atIndex:3];
        callback(expectedImage, nil, welf.smallImageURL, URL);
    });

    [imageProvider fetchImageForImageData:self.imageData size:self.smallImageSize withCompletionCallback:^(UIImage *anImage, id<BEImageAware> imageData, CGSize requestedSize) {

        OCMVerifyAll(cacheMock);
    }];
}

EXC_BAD_ACCESS happens here:

- (void)forwardInvocationForClassObject:(NSInvocation *)anInvocation
{
    // in here "self" is a reference to the real class, not the mock
    OCClassMockObject *mock = OCMGetAssociatedMockForClass((Class) self, YES);
    if(mock == nil)
    {
        [NSException raise:NSInternalInconsistencyException format:@"No mock for class %@", NSStringFromClass((Class)self)];
    }
    if([mock handleInvocation:anInvocation] == NO)
    {
        [anInvocation setSelector:OCMAliasForOriginalSelector([anInvocation selector])];
        [anInvocation invoke]; /// EXC_BAD_ACCESS
    }
}

The weird thing is that it never crashes when I run only this one test, but I crashes almost always when I tun all my tests (with cmd+u).

I tried to add [invocation retainArguments], it did not help, and I think should not be here. Anyone had such problems?

Is anything interesting in the stack trace of the failure? If you run all your tests except this one, do they consistently pass? — Ben Flynn, Jul 11 '15 at 04:23

score 2 · Answer 1 · answered Jul 06 '15 at 20:05

Given it is only failing when the tests are run together, it may be that one of the mock objects for a class you are testing remains after a particular test. For example, lets say your cacheMock is stubbing a method in a test (lets call it testOne).

After testOne is run, if you don't explicitly call [self.cacheMock stopMocking] at the end of it, the stub will still be on for the next test case, which may cause failures when trying to capture the arguments through the invocation.

In other words, verify that all your mocks are stopped in each test case, or at least the ones you may mock again. I would guess that either cacheMock or imageLoaderMock are causing the issue.

I though that I should only use `stopMocking` for partial mocks and when stubbing class methods. Is there a reason why `stopMocking` is also necessary for local mock variables? (I updated my question to make it clear that both `cacheMock` and `imageLoaderMock` are not partial mocks). And I tried adding `stopMocking ` calls, it did not help unfortunately — dariaa, Jul 07 '15 at 12:52

score 1 · Answer 2 · answered Jan 31 '18 at 14:03

I'm experiencing the same problem with OCMock 3.

I notice the crash was in the method stopMocking. According to OCMock docs "The mock automatically calls stopMocking during its own deallocation." (http://ocmock.org/reference/)

In my code, some methods execute other tasks in the background (using GCD), which may continue executing even after the test finishes. Therefore it was trying to access a mock that had already been deallocated and hence the crash. In order for the tasks to be completed, I added a timer in the tearDown method like this:

[NSThread sleepForTimeInterval:0.05];

This will give time for the tasks to execute before the mock is deallocated.

Hope this is helpful!

Random crash with OCMock

2 Answers2