How to deal with the test data in Junit?

Question

In TDD(Test Driven Development) development process, how to deal with the test data? Assumption that a scenario, parse a log file to get the needed column. For a strong test, How do I prepare the test data? And is it properly for me locate such files to the test class files?

Answer 1

Maven, for example, uses a convention for folder structures that takes care of test data:

src
  main
    java           <-- java source files of main application
    resources      <-- resource files for application (logger config, etc)
  test
    java           <-- test suites and classes
    resources      <-- additional resources for testing

If you use maven for building, you'll want to place the test resources in the right folder, if your building with something different, you may want to use this structure as it is more than just a maven convention, to my opinion it's close to 'best practise'.

Answer 2

Hard code them in the tests so that they are close to the tests that use them, making the test more readable.

Create the test data from a real log file. Write a list of the tests intended to be written, tackle them one by one and tick them off once they pass.

Answer 3

Another option is to mock out your data, eliminating any dependency on external sources. This way it's easy to test various data conditions without having to have multiple instances of external test data. I then generally use full-fledged integration tests for lightweight smoke testing.

Answer 4

When my test data must be an external file - a situation I try to avoid, but can't always - I put it into a reserved test-data directory at the same level as my project, and use getClass().getClassLoader().getResourceAsStream(path) to read it. The test-data directory isn't a requirement, just a convenience. But try to avoid needing to do this; as @philippe points out, it's almost always nicer to have the values hard-coded in the tests, right where you can see them.