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Mockito for Objective-C: creation, verification and stubbing of mock objects
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OCMockito is an Objective-C implementation of Mockito, supporting creation, verification and stubbing of mock objects.

Key differences from other mocking frameworks:

  • Mock objects are always "nice," recording their calls instead of throwing exceptions about unspecified invocations. This makes tests less fragile.

  • No expect-run-verify, making tests more readable. Mock objects record their calls, then you verify the methods you want.

  • Verification failures are reported as unit test failures, identifying specific lines instead of throwing exceptions. This makes it easier to identify failures. (It also keeps the pre-iOS 5 Simulator from crashing.)

Mac and iOS

Rather than build OCMockito yourself, I recommend you use the pre-built release available in Downloads. This works for projects using Automatic Reference Counting (ARC) as well as for projects using traditional memory management.

(But if you still want to build OCMockito yourself, go into the Source folder and execute from Terminal.)

The steps vary slightly depending on whether your project is a Mac project or an iOS project:


Add both OCHamcrest.framework and OCMockito.framework and to your project.

Add a Copy Files build phase to copy both OCHamcrest.framework and OCMockito.framework and to your Products Directory. For unit test bundles, make sure this Copy Files phase comes before the Run Script phase that executes tests.


#import <OCHamcrest/OCHamcrest.h>

#import <OCMockito/OCMockito.h>

Note: If your Console shows

otest[57510:203] *** NSTask: Task create for path '...' failed: 22, "Invalid argument". Terminating temporary process.

double-check your Copy Files phase.


Add both OCHamcrestIOS.framework and OCMockitoIOS.framework to your project.


#import <OCHamcrestIOS/OCHamcrestIOS.h>

#import <OCMockitoIOS/OCMockitoIOS.h>

Let's verify some behavior!

// mock creation
NSMutableArray *mockArray = mock([NSMutableArray class]);

// using mock object
[mockArray addObject:@"one"];
[mockArray removeAllObjects];

// verification
[verify(mockArray) addObject:@"one"];
[verify(mockArray) removeAllObjects];

Once created, the mock will remember all interactions. Then you can selectively verify whatever interactions you are interested in.

How about some stubbing?

// mock creation
NSArray *mockArray = mock([NSArray class]);

// stubbing
[given([mockArray objectAtIndex:0]) willReturn:@"first"];

// following prints "(null)" because objectAtIndex:999 was not stubbed
NSLog(@"%@", [mockArray objectAtIndex:999]);

How do you mock a class object?

Class mockStringClass = mockClass([NSString class]);

How do you mock a protocol?

id <MyDelegate> delegate = mockProtocol(@protocol(MyDelegate));

How do you mock an object that also implements a protocol?

UIViewController <CustomProtocol> *controller =
    mockObjectAndProtocol([UIViewController class], @protocol(CustomProtocol));

How do you stub methods that return non-objects?

To stub methods that return non-object types, specify willReturn<type>, like this:

[given([mockArray count]) willReturnUnsignedInteger:3];

Argument matchers

OCMockito verifies argument values by testing for equality. But when extra flexibility is required, you can specify OCHamcrest matchers.

// mock creation
NSMutableArray *mockArray = mock([NSMutableArray class]);

// using mock object
[mockArray removeObject:@"This is a test"];

// verification
[verify(mockArray) removeObject:startsWith(@"This is")];

OCHamcrest matchers can be specified as arguments for both verification and stubbing.

How do you specify matchers for primitive arguments?

To stub a method that takes a primitive argument but specify a matcher, invoke the method with a dummy argument, then call -withMatcher:forArgument:

[[given([mockArray objectAtIndex:0]) withMatcher:anything() forArgument:0]

Use the shortcut -withMatcher: to specify a matcher for a single argument:

[[given([mockArray objectAtIndex:0]) withMatcher:anything()]

Verifying exact number of invocations / at least x / never

// using mock
[mockArray addObject:@"once"];

[mockArray addObject:@"twice"];
[mockArray addObject:@"twice"];

// the following two verifications work exactly the same
[verify(mockArray) addObject:@"once"];
[verifyCount(mockArray, times(1)) addObject:@"once"];

// verify exact number of invocations
[verifyCount(mockArray, times(2)) addObject:@"twice"];
[verifyCount(mockArray, times(3)) addObject:@"three times"];

// verify using never(), which is an alias for times(0)
[verifyCount(mockArray, never()) addObject:@"never happened"];

// verify using atLeast
[verifyCount(mockArray, atLeastOnce()) addObject:@"at least once"];
[verifyCount(mockArray, atLeast(2)) addObject:@"at least twice"];

More resources

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