jar-with-dependencies: class from the source in project does NOT override the class in jar dependency

When running plugin maven-assembly-plugin 2.2.1 with jar-with-dependencies, and there is a class C1 in src/main/java/ that overrides a class C1 in some dependency, in the resulting XXX-jar-with-dependencies.jar the C1.class comes from the dependency, not from the source in project.
I would except the class from the source in project to override the corresponding class in jar dependency,
So the executable jar is not built correctly. This is particularly annoying, because the tests pass, but the executable jar is not correct.

You can see this in the test project attached, where I override class TestCase of JUnit , adding a main , and setting this overriden class as the main class:

% java -jar target/maven_bug_build_override_class-1.0-SNAPSHOT-jar-with-dependencies.jar
Exception in thread "main" java.lang.NoSuchMethodError: main
( the original class TestCase of JUnit has no main ).

In the test project attached,I kept all the Maven plugins that are in my original project, because they might have a relation with the issue.