Separation of JUnit classes into special test package?

Question

I am learning the concepts of Test-Driven Development through reading the Craftsman articles (click Craftsman under By Topic) recommended in an answer to my previous question, "Sample project for learning JUnit and proper software engineering". I love it so far!

But now I want to sit down and try it myself. I have a question that I hope will need only a simple answer.

How do you organize your JUnit test classes and your actual code? I'm talking mainly about the package structure, but any other concepts of note would be helpful too.

Do you put test classes in org.myname.project.test.* and normal code in org.myname.project.*? Do you put the test classes right alongside the normal classes? Do you prefer to prefix the class names with Test rather than suffix them?

I know this seems like the kind of thing I shouldn't worry about so soon, but I am a very organization-centric person. I'm almost the kind of person that spends more time figuring out methods to keep track of what to get done, rather than actually getting things done.

And I have a project that is currently neatly divided up into packages, but the project became a mess. Instead of trying to refactor everything and write tests, I want to start fresh, tests first and all. But first I need to know where my tests go.

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edit: I totally forgot about Maven, but it seems a majority of you are using it! In the past I had a specific use case where Maven completely broke down on me but Ant gave me the flexibility I needed, so I ended up attached to Ant, but I'm thinking maybe I was just taking the wrong approach. I think I'll give Maven another try because it sounds like it will go well with test-driven development.

Answer 1

I prefer putting the test classes into the same package as the project classes they test, but in a different physical directory, like:

myproject/src/com/foo/Bar.java
myproject/test/com/foo/BarTest.java

In a Maven project it would look like this:

myproject/src/main/java/com/foo/Bar.java
myproject/src/test/java/com/foo/BarTest.java

The main point in this is that my test classes can access (and test!) package-scope classes and members.

As the above example shows, my test classes have the name of the tested class plus Test as a suffix. This helps finding them quickly - it's not very funny to try searching among a couple of hundred test classes, each of whose name starts with Test...

Update inspired by @Ricket's comment: this way test classes (typically) show up right after their tested buddy in a project-wise alphabetic listing of class names. (Funny that I am benefiting from this day by day, without having consciously realized how...)

Update2: A lot of developers (including myself) like Maven, but there seems to be at least as many who don't. IMHO it is very useful for "mainstream" Java projects (I would put about 90% of projects into this category... but the other 10% is still a sizeable minority). It is easy to use if one can accept the Maven conventions; however if not, it makes life a miserable struggle. Maven seems to be difficult to comprehend for many people socialized on Ant, as it apparently requires a very different way of thinking. (Myself, having never used Ant, can't compare the two.) One thing is for sure: it makes unit (and integration) testing a natural, first-class step in the process, which helps developers adopt this essential practice.

Answer 2

I put my test classes in the same package as what they are testing but in a different source folder or project. Organizing my test code in this fashion allows me to easily compile and package it separately so that production jar files do not contain test code. It also allows the test code to access package private fields and methods.

Answer 3

I use Maven. The structure that Maven promotes is:-

src/main/java/org/myname/project/MyClass.java

src/test/java/org/myname/project/TestMyClass.java

i.e. a test class with Test prepended to the name of the class under test is in a parallel directory structure to the main test.

One advantage of having the test classes in the same package (not necessarily directory though) is you can leverage package-scope methods to inspect or inject mock test objects.