Support XCTest, Expecta and Nimble assertions in Kiwi specs

[sharplet]

This change allows the use of XCTest assertions in specs. This should hopefully include other matcher libraries implemented in terms of XCTest assertions!

To be clear, I'm thinking of adding some more functional specs in this PR to test out whether this will enable support for Expecta or Nimble matchers.

This now works:

#import <Kiwi/Kiwi.h>

SPEC_BEGIN(KWObjCXCTestAssertionTests)

describe(@"XCTest assertions in Objective C", ^{
    it(@"supports XCTAssert", ^{
        XCTAssert(1 + 1 == 3); // <- fails with a real test failure instead of an exception or warning!
    });
});

SPEC_END

---

• Within +buildExampleGroups, defines a shadow self pointer that is of the type of the test case instance.
• Unrecognized selectors sent to the test case class are forwarded to
  the current example, and then to the current test case instance.
• Adds a test for the use of XCTest assertions within specs.

This should possibly be considered a breaking change, because any users depending on the type of self being their test case class (and for example invoking class methods on KWSpec different in a category) will now get compiler warnings (that would be compiler errors in the case of -Werror).

However:

• This will just generate compiler warnings that could safely be ignored, as the tests themselves won't fail because self is still actually the class object at runtime!
• It should be fairly straightforward to redefine any of those class methods as instance methods.
• While valid code, it's not an encouraged or documented way of writing test helper methods.

To make this not a breaking change (at compile time), a workaround could be for this PR to change the type of self to id. This is probably even more accurate! However the convenience of the static type declaration is useful. I just don't know if this will be an issue in practice for Kiwi users.

[sharplet]

This test passes. In fact, it probably would have passed without any of the other changes in this PR. 0_o

The important thing is actually not that this test passes, but that when it fails it fails in the right way. I don't actually know how to verify that. ¯_(ツ)_/¯

[supermarin]

👍 for the code.
Will give it a bit of thought on how to test your assertion

[sharplet]

I've just pushed a couple more commits adding explicit support for both Expecta and Nimble matchers!

[sharplet]

Been thinking on testing that assertions behave correctly, and I could potentially follow a similar approach to this: https://github.com/kiwi-bdd/Kiwi/blob/master/test_suite_configuration.rb.

Basically:

• Create a separate test bundle for testing matcher failures, and move the XCTest, Expecta and Nimble specs there.
• Write a script that matches on the output of running that test bundle.
• Integrate the script into CI.

However, it would be a lot nicer to have it properly integrated into the existing test suite.

[sharplet]

Yo @supermarin, came up with something for testing that assertions occur: a77c3e7.

[supermarin]

[sharplet]

I looked into trying to do write the same kind of test in the Swift specs, but we don't even support full Kiwi matchers in Swift yet. And it's working really well in Objective-C, so I don't think it's necessary to duplicate the effort in this PR.

⛵

[aspcartman]

It's not working for me

#import <Kiwi/Kiwi.h>
#import <Expecta/Expecta.h>

SPEC_BEGIN(TestSpec)

describe(@"Just a test", ^{
    it(@"Works",^{
        expect(1).to.equal(1);
    });
});

SPEC_END

It errors on Expecta/EXPMatchers+beNil.h on (3,21): expected ')'