Migrate to Latest OCMock, Demonstrate Improved Unit Testing

[Adlai-Holler]

Unit tests are great! tl;dr: This diff migrates us from OCMock 2.2 to 3.4, and migrates ASMultiplexImageNodeTests to the latest syntax as a demonstration.

• The new version of OCMock supports a great new syntax, and prints much better error messages.
• There's no urgency to migrate the rest of our existing test cases. I migrated the multiplex image node tests only to provide a better reference for future test development.
• Recommend you use split diff for the multiplex image node tests file since it's changed a lot. The spirit/intention of each test method is preserved.
• The migration of the multiplex image node tests revealed a minor bug.
  • Namely that we call imageForImageIdentifier: twice if the first time it returns nil. Now [ASMultiplexImageNode] imageForImageIdentifier: Method May Be Called Multiple Times if First Call Returns Nil #346.
  • Bug itself isn't interesting, but the total failure of our previous unit tests to catch it, is.
• New syntax is much more readable:
  • Old: [[[mockCache expect] andDo:^(NSInvocation *inv) { … }] imageForImageID:OCMOCK_ANY];
  • New: OCMExpect([mockCache imageForImageID:OCMOCK_ANY]).andDo(^(NSInvocation *inv) { … });
• NSInvocation+OCMAdditions file is no longer public, so I created a mini version of those methods NSInvocation+ASTestHelpers that is actually safer under ARC.
• New pattern established in multiplex image node tests is much tighter and cleaner:
  • -tearDown includes OCMVerifyAll of all mocks created in -setUp.
    • Test methods just have to OCMExpect and run their code, validation is done for them.
  • -setUp sets expectationOrderMatters on all mocks. Test methods can clear this flag if they need to, but they shouldn't.
  • Stubbing is used very sparingly (one place), since it doesn't make any assertion about when the method is called. Use OCMExpect instead, unless you're really sure the method sequence is irrelevant.
  • Test case ivars do not have underscores: _mockCache -> mockCache.
    • Breaks from tradition but is readable and reduces boilerplate inside test methods.

Note: The indentation style for chained macros may seem strange to you (I quite like it), but it's the Xcode default:

OCMExpect([mockDataSource multiplexImageNode:imageNode imageForImageIdentifier:highResIdentifier])
.andReturn([self _testImage]);

[Adlai-Holler]

Unfortunately, under the new OCMock, if an exception is thrown while inside a mock object method, and you later verify, it will fail and report that an exception was thrown. So we will have to avoid verifying after testing exception-throwing, which is sucky but not worth holding back on OCMock 2.2.

[maicki]

Nice - And the I really like the new syntax!