We are implementing a functional/regression testing system at work to test our services (our app is setup using a client/server architecture).
How do you start? Do you build some test cases? What about starting a new feature? Would all the test cases go into one file (we are using mocha and node.js)?
For regressions, you should start from the parts of your system that actually work and show no bugs. You write some test cases against that part, and re-do them on future relases to ensure that the application is always working in the right way.
http://en.wikipedia.org/wiki/Regression_testing
I suggest using some form of automation, to ensure you always do the same checks in the exact way. Here's a list of common used softwares
http://en.wikipedia.org/wiki/Test_automation#Notable_test_automation_tools
