Unit Testing or Functional Testing? [closed]

Answer 1

Functional testing, also called System testing, aims at testing the complete system, and verifying the functional requirements are satisfied.

Unit testing aims at testing the "units", i.e. the functions or methods the system is build from in isolation. It's sometimes called Developer testing. Unit testing can be hard after the fact, that's why TDD writes the test before the code.

Those are complementary as the units can work independently and not when integrated all together, or they can pass the unit tests, and not fulfill all the product requirements.

Answer 2

• Unit test = lowest, granular level.
• Functional test = middling, modular level.
• Integration test = higher application level.
• Factory Acceptance Test = see it all work
• Site Acceptance Test = see it all fail :)

All the above are useful but they're not mutually exclusive. You should be doing most of them but the amount of time you spend on each part depends on the results you get from them, that's all. If your code is too modular to be easily unit tested, then spend your efforts on the functional tests. If you're writing a library of small components, spend your time on unit testing them, and if you're writing control systems for military missiles you should definitely be site acceptance testing them (as explosions even when it fails is fun :) )