The OCExpectations project provides a library of Objective-C expectation matchers styled after RSpec expectations. Expressing an expectation in Ruby RSpec as
5.should equal(5)becomes
[@5 should:[@5 equal]]in Objective-C. Very similar albeit in a somewhat Shakespearean form of words. Or perhaps Yoda-speak would be a better analogy; although he would more likely say, "equal 5, 5 should!" Nevertheless, Objective-C's receiver-message syntax dictates the ordering. The -should:aMatcher message describes a positive expectation while -equal specifies the equality matcher.
Does this improve over using C functions and macros for matchers?
Yes with respect to namespaces. The project could define a pre-processor macro, or function, so that your expectation would read [@5 should:equal(@5)] for example. Trouble is, Objective-C has no namespace or module support. The matcher macros would consequently live in the global namespace and potentially clash with other projects including your own. What if your project defines equal? Adding a namespace prefix, as is convention, would work around that issue. But [@5 should:OCSpecEqual(@5)] looses something in readability.
The same applies to some extent with the expectation interface, -[NSObject should:aMatcher]. This polutes the NSObject space. What if your project defines that method on NSObject or one of its subclasses? Trouble at mill!
As a compromise, OCExpectations hash-defines a set of corresponding C pre-processor macros if and only if not already defined. So if your or some other included project defines be then you cannot use be(@5) and have to use [@5 be]. Provided that you import <OCExpectations/OCExpectations.h> at the very end of your list of imports, then namespace collisions will never occur and you can enjoy the more natural form of expression:
[@5 should:equal(@5)]The above example makes use of the Objective-C literal syntax available in the LLVM version 4.0 compiler bundled with Xcode 4.4 and above. You consequently need LLVM version 4.0 as a minimum requirement, as the project source code makes full use of literals and boxed expressions.
You can easily expand on the library by adding your own matchers.
The OC namespace stands for Objective-C of course but it carries additional significance. This choice reflects the project goals of cross platform support and open-source community responsibility. The info.rspec.OCExpectations bundle identifier echoes the same aspiration.
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