You could have downloaded Randoop 3.1.5 for Mac from our software library for free. The actual developer of this free Mac application is Carlos Pacheco. Randoop for Mac is included in Developer Tools.
From the developer:
Randoop generates unit tests using feedback-directed random test generation. This technique randomly, but smartly, generates sequences of method/constructor invocations for the classes under test. Randoop executes the sequences it creates, using the results of the execution to create assertions that capture the behavior or your program. Randoop creates tests from the code sequences and assertions.
You may want to check out more Mac applications, such as FMMenulet, eclipse-php or Prototypes, which might be related to Randoop.