Eclipse/Maven: JUnit tests not compiled when running them

I am working on a project using Maven and Eclipse (m2eclipse plugin). I've got problems with the JUnit tests:

Sometimes, when running them within Eclipse, they wont be compiled, but the old class files are used instead. When I delete the class files, I get ClassNotFoundExceptions in Eclipse. I then have to manually recompile them by using mvn test-compile or other goals.

I also noticed that the class files of the tests sometimes are put into the classes subdirectory instead of test-classes.

I really can't figure out what is wrong.

The JUnit java files are within src/main/java and are correctly named (*Test.java).

Do I have to compile and run them always via Maven? Why doesn't Eclipse compile the files when I want to run them? (Interestingly, sometimes it does. Sometimes everything works perfectly.)

Solution 1:

I had the same problem with STS Eclipse (Spring development variant), m2e and JUnit. The solution was to set the output folder for src/test/java to target/test-classes:

1. Right click the src/test/java folder in the Package Explorer
2. Select Build Path -> Configure Output Folder
3. Enter target/test-classes, click OK

Now the changes in test classes are compiled correctly and you should be able to run JUnit tests in Eclipse.

The problem is that Eclipse compiles the unit tests to the default output folder target/classes while JUnit plugin correctly tries to run them from test-classes.

There are a few duplicates to this question:

• ClassNotFoundException when running JUnit unit tests within Eclipse (using Maven)
• Eclipse doesn't see my new junit test
• junit not using the newest file

Solution 2:

In addition to the answer below

1. Right click the src/test/java folder
2. Select Build Path -> Configure Output Folder
3. Enter target/test-classes, click OK

you should check to ensure that your builder is setup correctly by right clicking your project and going to Properties -> Builder. If you see that your builder is missing, you need to install one. In my case, the maven project had an AspectJ dependency and when I used the Maven Eclipse plugin to build my Eclipse project, it was looking for an AspectJ builder by default. I installed the AspectJ development tools and it solved the problem.

Hope this helps!

Solution 3:

The most likely explanations for the problem you are facing is that the output folder of src/test/java is not correctly configured.

Instead of fixing this configuration manually, you can have m2eclipse fix this for you: Just right-click on the project and choose Maven > Update Project.

Solution 4:

And another point: JUnit test classes should be in src/test/java, not src/main/java, otherwise they aren't detected correctly by Maven as test classes and they would be included in the packaged jar and not in the test jar.