TestKit Documentation
A Suite is a collection of test cases. A TWTestSuite can be constructed from a subclass of TWTestCase or an instance of NSBundle. In addition, you can create an empty suite and add tests to it manually. Please see the documentation for details.

Note that suites are used as an organizational tool for the developer. They are optional. The tools provided with TestKit to run tests will automatically create test suites from the bundles they run. By default, the order of execution of these tests are undefined. If you need to organize your tests in an order different than that generated by the testing tools, you are encouraged to manually define your own suites.