The 0.9 version of TestKit for Mac was available to download on the developer's website when we last checked. We cannot confirm if there is a free download of this app available. We recommend checking the downloaded files with any free antivirus. The software lies within Education Tools, more precisely Reference.
From the developer:
TestKit from ThoughtWorks is a testing framework for Mac OS X and the Objective-C language. Modeled after JUnit, it allows Mac OS X developers working in the Cocoa environment to write unit tests against Objective-C objects and features both command-line and graphical test running tools.
You may want to check out more software for Mac, such as SGDVLite, which might be related to TestKit.
Debugging Tools