OCMock - Block Testing

### Features

• [OCMArg invokeBlock]

  • A constraint specific to block arguments.
  • It auto-invokes the block with default values for each of its arguments.
  • E.g. OCMStub([uiView animateWithDuration:0.4 animations:[OCMArg invokeBlock] completion:[OCMArg invokeBlock]]).

• [OCMArg invokeBlockWithArgs:...]

  • A constraint specific to block arguments.
  • It auto-invokes the block with the given values for each of its arguments.
  • The number of arguments passed in the vargs must match the number of arguments that the block takes.
  • The type of the arguments passed in the vargs must be compatible with the types of the arguments that the block takes.
  • Argument values which are not Objective-C objects (e.g. primitives, structs, pointers) must be boxed in NSValue.
  • Use OCMOCK_VALUE to do this conveniently.
  • Pass OCMDefault in the vargs to invoke the block with a default argument.
  • List of arguments must be nil-terminated.
  • Note that it requires additional parentheses when used in an OCMStub macro to avoid the vargs being parsed as separate macro arguments.
  • E.g. OCMStub([obj doSomethingComplexCompletionBlock:([OCMArg invokeBlockWithArgs:@"A first param", @123, OCMOCK_VALUE(somePtr), OCMDefault, nil])])

### Use Cases

• UIViewController transition methods
• UIView animation methods
• Third party dependencies, e.g. RestKit
• NSArray enumeration methods

Tests

• This repo contains 2 test harnesses:

  • Strange Types, which tests these features out with all sorts of obscure block signatures,
  • A sample application taken from BetweenKit, which aims to demonstrate how this feature might be used in the real world.

• All tests have passed on the following:

  • iPhone 6, iOS 8.3
  • iPad Mini, iOS 8.1
  • iPad 2, iOS 8.3
  • iPad 2 Simulator, iOS 7.1, iOS 8.1, iOS 8.4
  • iPad Retina Simulator, iOS 7.1, iOS 8.1, iOS 8.4

• Tests in my OCMock fork have passed on the following:

  • Macbook Pro, Retina 15", OS X Yosemite 10.10.4

### Limitations

• This relies on NSInvocation to invoke the blocks and as a result, does not support va_lists or unions as arguments.
• This has not been tested with function pointers as block arguments.
• OCMBlockArgCaller is quite strict: it will throw if the type signature of a given argument doesn't match the type signature of the block (to offer as much feedback as possible to the user).

### References

• This article
• CTObjectiveCRuntimeAdditions
• BlocksKit/DynamicDelegate