Thursday, December 28, 2006


Test Driven Development

  • The importance of writing tests
    • They force the developer to think of the class design
    • They provide a safety harness while refactoring
    • They ensure that the state of code is always stable
    • New developers can make changes comfortable with the knowledge that if they break something that was working, the tests will inform them
    • Test after development is not the same as test first development. Test after development does not reap all the benefits of test first development
  • Writing the tests
    • Think about the class it’s responsibilities and it’s API
    • Write the tests to test every method and various conditions in the methods
    • Whenever you think of writing a print statement or generate a log, it might be a scenario to include a test
    • Write enough production code to ensure that the tests compile and fail
    • Write production code to pass all tests one by one, while also ensuring that previous tests do not fail
  • What not to test
    • Database entities need not be tested
    • Do not go overboard with tests. First write tests that are most likely to fail. Think of the cost benefit ratio while writing tests
  • The test class
    • Tests classes end with the work Test. The test class for Account will be AccountTest
    • Test methods begin with the word test. The test method for creditAccount() will be testcreditAccount()
    • Tests can either exist in a different source tree in the same package as the class they are testing, or in the same source tree, but in a different package.
  • Managing dependencies
    • Unit tests should ideally not have any dependencies
    • Dependencies can be eliminated with mock objects (so that units can be tested in isolation)
  • AllTests
    • There should have one class AllTests that will run the entire test suite

    Requirements (Java Unit Tests):

    • JUnit 3.8 for JDK 1.4 and before
    • JUnit 4.x for JDK 1.5 and after
    • StrutsTestCase for testing Struts Action classes


Notes: This text was originally posted on my earlier blog at


Aditi said...

Very nice insight on TDD.

Parag said...

Thanks Aditi