The best way for a new developer to get to know the domain model and to understand the business rules is to read through the test suite first. From there the n

The best way for a new developer to get to know the domain model and to understand the business rules is to read through the test suite first. From there the new developer may read through the implementation of the domain objects, controllers, etc. This assumes, of course, that the application is well designed, continually refactored and well tested. Every app has skeletons in the closet, though, and this perfect world often leaves something to be desired. If your code is relatively clean though, you'll have one and only one place where you instruct an account to be invoiced, and you can trace through that code anytime you have questions about how that scenario works. Suggestion: Every time you go diving into the code to investigate some scenario and wish to discover the business rules, start by writing a test for it. Write tests that expect that behavior, then execute the scenario and ensure your tests pass. Better yet, write those test first and you're all the way there. :)