Eclipse junit testing in the same project

While there is no only right way, the usual approach is to keep unit tests in the same project.

You can create a second source folder (like test), where you put your test classes into the same packages as the classes under test. This also allows you to test package-private classes while not flooding your main source packages with test classes.

Your source folder/package structure would then look like this:

-sources
   -main
       -my.package
             -MyClass.java
   -test
       -my.package
             -MyClassTest.java

You can then configure your build to not include the test source folder when packing the JAR.