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https://github.com/jonreid/OCMockito

Mockito for Objective-C: creation, verification and stubbing of mock objects
https://github.com/jonreid/OCMockito

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Mockito for Objective-C: creation, verification and stubbing of mock objects

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# OCMockito



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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.



## Contents



  * [Let's verify some behavior!](#lets-verify-some-behavior)

  * [How about some stubbing?](#how-about-some-stubbing)

  * [How do you mock a class object?](#how-do-you-mock-a-class-object)

  * [How do you mock a protocol?](#how-do-you-mock-a-protocol)

  * [How do you mock an object that also implements a protocol?](#how-do-you-mock-an-object-that-also-implements-a-protocol)

  * [How do you stub methods that return primitives?](#how-do-you-stub-methods-that-return-primitives)

  * [How do you stub methods that return structs?](#how-do-you-stub-methods-that-return-structs)

  * [How do you stub a property so that KVO works?](#how-do-you-stub-a-property-so-that-kvo-works)

  * [Argument matchers](#argument-matchers)

  * [How do you specify matchers for non-object arguments?](#how-do-you-specify-matchers-for-non-object-arguments)

  * [Verifying exact number of invocations / at least x / never](#verifying-exact-number-of-invocations--at-least-x--never)

  * [Capturing arguments for further assertions](#capturing-arguments-for-further-assertions)

  * [Stubbing consecutive calls](#stubbing-consecutive-calls)

  * [Stubbing with blocks](#stubbing-with-blocks)

  * [Problems with dealloc](#problems-with-dealloc)

  * [How do you mock a singleton?](#how-do-you-mock-a-singleton)

  * [How do I add OCMockito to my project?](#how-do-i-add-ocmockito-to-my-project)

    * [Swift Package Manager](#swift-package-manager)

    * [CocoaPods](#cocoapods)

    * [Carthage](#carthage)

    * [Prebuilt Framework](#prebuilt-framework)

    * [Build Your Own](#build-your-own)

  * [Author](#author)



## Let's verify some behavior!



```obj-c

// 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.



(If Xcode complains about multiple methods with the same name, cast `verify`

to the mocked class.)



## How about some stubbing?



```obj-c

// mock creation

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



// stubbing

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

[given([mockArray objectAtIndex:1]) willThrow:[NSException exceptionWithName:@"name"

                                                                      reason:@"reason"

                                                                    userInfo:nil]];



// following prints "first"

NSLog(@"%@", [mockArray objectAtIndex:0]);



// follows throws exception

NSLog(@"%@", [mockArray objectAtIndex:1]);



// following prints "(null)" because objectAtIndex:999 was not stubbed

NSLog(@"%@", [mockArray objectAtIndex:999]);

```



## How do you mock a class object?



```obj-c

__strong Class mockStringClass = mockClass([NSString class]);

```



(In the iOS 64-bit runtime, Class objects aren't strong by default. Either make

it explicitly strong as shown above, or use `id` instead.)



## How do you mock a protocol?



```obj-c

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

```



Or, if you don't want it to contain any optional methods:



```obj-c

id  delegate = mockProtocolWithoutOptionals(@protocol(MyDelegate));

```



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



```obj-c

UIViewController  *controller =

    mockObjectAndProtocol([UIViewController class], @protocol(CustomProtocol));

```



## How do you stub methods that return primitives?



To stub methods that return primitive scalars, box the scalars into NSValues:



```obj-c

[given([mockArray count]) willReturn:@3];

```



## How do you stub methods that return structs?



Use `willReturnStruct:objCType:` passing a pointer to your structure and its

type from the Objective-C `@encode()` compiler directive:



```obj-c

SomeStruct aStruct = {...};

[given([mockObject methodReturningStruct]) willReturnStruct:&aStruct

                                                   objCType:@encode(SomeStruct)];

```



## How do you stub a property so that KVO works?



Use `stubProperty(mock, property, stubbedValue)`. For example, say you have a

mock object named `mockEmployee`. It has a property `firstName`. You want to

stub it to return the value "FIRST-NAME":



```obj-c

stubProperty(mockEmployee, firstName, @"FIRST-NAME");

```



This stubs the `firstName` property, `valueForKey:` and `valueForKeyPath:`.



## Argument matchers



OCMockito verifies argument values by testing for equality. But when extra

flexibility is required, you can specify

 [OCHamcrest](https://github.com/hamcrest/OCHamcrest) matchers.



```obj-c

// 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.



Typed arguments will issue a warning that the matcher is the wrong type. Just

cast the matcher to `id`.



## How do you specify matchers for non-object arguments?



To stub a method that takes a non-object argument but specify a matcher, invoke

the method with a dummy argument, then call `-withMatcher:forArgument:`



```obj-c

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

 willReturn:@"foo"];

```



This is particularly useful for ignoring `NSError **` parameters: pass in `NULL`, but override it with an `anything()` matcher.



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



```obj-c

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

 willReturn:@"foo"];

```



These methods are also available to specify matchers for verification. Just call

them after `verify(…)` but before the invocation you want to verify:



```obj-c

[[verify(mockArray) withMatcher:greaterThan(@5])] removeObjectAtIndex:0];

```



## Verifying exact number of invocations / at least x / never



```obj-c

// 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()/atMost()

[verifyCount(mockArray, atLeastOnce()) addObject:@"at least once"];

[verifyCount(mockArray, atLeast(2)) addObject:@"at least twice"];

[verifyCount(mockArray, atMost(5)) addObject:@"at most five times"];

```



## Capturing arguments for further assertions



OCMockito verifies argument values using OCHamcrest matchers; non-matcher

arguments are implicitly wrapped in the `equalTo` matcher to test for equality.

In some situations though, it's helpful to capture an argument so you can send

it another message.



OCHamcrest provides a special matcher for this purpose: HCArgumentCaptor.

Specify it as an argument, then query it with either the `value` or `allValues`

properties.



For example, you may want to send the captured argument a message to query its

state:



```obj-c

HCArgumentCaptor *argument = [[HCArgumentCaptor alloc] init];

[verify(mockObject) doSomething:(id)argument];

assertThat([argument.value nameAtIndex:0], is(@"Jon"));

```



Capturing arguments is especially handy for block arguments. Capture the

argument, cast it to the block type, then invoke the block directly to simulate

the ways it will be called by production code:



```obj-c

HCArgumentCaptor *argument = [[HCArgumentCaptor alloc] init];

[verify(mockArray) sortUsingComparator:(id)argument];

NSComparator block = argument.value;

assertThat(@(block(@"a", @"z")), is(@(NSOrderedAscending)));

```



## Stubbing consecutive calls



```obj-c

[[given([mockObject someMethod:@"some arg"])

    willThrow:[NSException exceptionWithName:@"name" reason:@"reason" userInfo:nil]]

    willReturn:@"foo"];



// First call: throws exception

[mockObject someMethod:@"some arg"];



// Second call: prints "foo"

NSLog(@"%@", [mockObject someMethod:@"some arg"]);



// Any consecutive call: prints "foo" as well. (Last stubbing wins.)

NSLog(@"%@", [mockObject someMethod:@"some arg"]);

```



## Stubbing with blocks



We recommend using simple stubbing with `willReturn:` or `willThrow:` only. But

`willDo:` using a block can sometimes be helpful. The block can easily access

invocation arguments by calling `mkt_arguments` from NSInvocation+OCMockito.h.

Whatever the block returns will be used as the stubbed return value.



```obj-c

[given([mockObject someMethod:anything()]) willDo:^id (NSInvocation *invocation){

    NSArray *args = [invocation mkt_arguments];

    return @([args[0] intValue] * 2);

}];



// Following prints 4

NSLog(@"%@", [mockObject someMethod:@2]);

```



You can stub a void method with a block by using `givenVoid` instead of `given`.



## Problems with dealloc



Use `stopMocking(…)` if a `-dealloc` of your System Under Test is trying to

message an object that is mocked. It disables message handling on the mock and

frees its retained arguments. This prevents retain cycles and crashes during

test clean-up. See StopMockingTests.m for an example.



## How do you mock a singleton?



The short answer is: Don't. Instead of your class deciding who it's going to

talk to, inject those dependencies.



The longer answer is: Well. Legacy code. Call `stubSingleton` on a mock class

object, specifying the name of the factory method.



```obj-c

__strong Class mockUserDefaultsClass = mockClass([NSUserDefaults class]);

NSUserDefaults* mockDefaults = mock([NSUserDefaults class]);



stubSingleton(mockUserDefaultsClass, standardUserDefaults);

[given([NSUserDefaults standardUserDefaults]) willReturn:mockDefaults];

```



Beware! This uses swizzling. You need to make sure the mock class object gets

deallocated so that the swizzling is undone.



In the example above, `mockUserDefaultsClass` will go out scope and be

destroyed. But what if you kept it in the test fixture, as an ivar or a

property? According to XCTest's design, it won't be implicitly destroyed.

You need to explicitly set it to nil in `-tearDown`, or the swizzling will

bleed over to your other tests, compromising their integrity.



If you need more control over when the swizzling is undone, call

`stopMocking(…)` on the mock class.



## How do I add OCMockito to my project?



The [Examples](https://github.com/jonreid/OCMockito/tree/main/Examples) folder shows projects

ready to use OCMockito via Swift Package Manager, CocoaPods, or through the prebuilt framework.



### Swift Package Manager



Include an OCMockito package in your Package.swift manifest's array of `dependencies`:





```swift

dependencies: [

    .package(

        url: "https://github.com/jonreid/OCMockito",

        .upToNextMajor(from: "7.0.0")

    ),

],

```

snippet source | anchor



Then add OCMockito to the dependencies of your `.testTarget`:





```swift

.testTarget(

    name: "ExampleTests",

    dependencies: [

        "Example",

        "OCMockito",

    ]

),

```

snippet source | anchor



### CocoaPods



If you want to add OCMockito using Cocoapods then add the following dependency

to your Podfile. Most people will want OCMockito in their test targets, and not

include any pods from their main targets:



```ruby

target 'MyTests' do

  inherit! :search_paths

  use_frameworks!

  pod 'OCMockito', '~> 7.0'

end

```



### Carthage



Add the following to your Cartfile:



```

github "jonreid/OCMockito" ~> 7.0

```



Then drag the the built frameworks (both OCHamcrest and OCMockito) from the

appropriate Carthage/Build directory into your project, but with "Copy items

into destination group's folder" disabled.



### Prebuilt Framework



A prebuilt binary is available on GitHub for

[OCMockito](https://github.com/jonreid/OCMockito/releases/). You will also need

[OCHamcrest](https://github.com/hamcrest/OCHamcrest/releases/).

The binary is packaged as OCMockito.xcframework, containing these architectures:

* macOS

* Mac Catalyst

* iOS device

* iOS simulator

* tvOS device

* tvOS simulator

* watchOS device

* watchOS simulator



Drag the XCFramework into your project.



### Build Your Own



If you want to build OCMockito yourself, clone the repo, then



```sh

$ cd Source

$ ./MakeDistribution.sh

```



## Author



Jon Reid is the author of _[iOS Unit Testing by Example](https://iosunittestingbyexample.com)._ His website is [Quality Coding](https://qualitycoding.org).