"Class not found" when run/debug JUnit tests

The proposed workaround doesn't work for me. Hence, it seems to be something else causing the problem.
Sadly, I haven't been able to gain much more information.

However, I followed the instructions in the mailing list thread mentioned in the description and came to the conclusion that there is no significant difference between the command line when the JUnit tests runs normally and when NoClassDefFoundError are thrown. The once chance is the port and testName filename.

Quite annoying bug since there isn't a known workaround. I'll be glad to investigate further if I get some instructions.

Eugene or other person in the Maven 2.x Eclipse Plugin team,

are you not experiencing this problem? I see it quite often and it's causing a lot of head-ache.
I would gladly provide more information if I know what to look for.

Cannot reproduce. Require a sample project attachment that reproduces this problem.

Our environment is susceptible to this enviroment as well using Eclipse 3.2 and the Maven2 Eclipse Plugin 0.0.9. I have been able to create a small test case the mirrors our environment. We separate our projects into both a source and a test project. We do this because we weave different aspects in our production and test environments. However, this configuration does expose the problem.

The two projects included in the following attachment are a source (maven-sample) project and a test (maven-sample-test) project. If the JUnit dependency is removed from the maven-sample project, the NoClassDefFoundError appears when attempting to run the test cases. If the JUnit dependency is present in the maven-sample project, then the test cases can be run. However, this "trick" does not work for our configuration.

I was also able to get Diego's suggestion to work if I added a Maven2 Dependencies above the JRE System Library in the Classpath -> Bootstrap Entries of the target I was trying to run. However, this is less than ideal if you wish to choose a single test case to execute.

Two Eclipse projects (maven-sample and maven-sample-test) to reproduce the problem.

Our project structure is organized into a hierarchy of projects. I have found that the complete set of libraries needs to be specified for each of the individual projects. In other words, if Project A needs libraries aa, ab, ac and Project B needs ba, bb, bc, you would need to specify aa, ab, ac, ba, bb, bc for both Project A and Project B. Looks like the plugin might be having trouble determining library dependencies.

I can't add much value to what has already been said, but this issue is absolutely killing me. I'll be happy to pitch in and try anything to help diagnose it. The suggested workaround doesn't work for me.

This bug is a killer. When trying to run JUnit test using Eclipse's JUnit launcher I've discovered that none of jars (beside Junit jar) from 'Maven dependencies' is in the classpath of JUnit test - producing java.lang.NoClassDefFoundError for every one of my spring-driven tests. This practically renders Eclipse-Maven integration useless for a person using TDD .

I've had the same issue. I checked the eclipse problems view for that project and apparently there was a duplicate library on the build path.
After that i removed all the classpath entries that started with M2_REPO and now it works fine.

All the neccesary dependencies were already on the build path (under maven 2 dependencies) so why are there extra build path entries?

Anyway that solved the problem for me.

Dude, can someone please fix this. It's killing me.
I can't junit my projects. My productivity is down the drain.
Thanks,
--jim

I was able to fix by running "update source folders" on all related projects.

only one thing worked for me: running "mvn clean test" from shell before (one time only) and then tests can run in eclipse normally

I do not thing this is a bug. It's a issue with eclipse not noticing that mvn has rebuilt it all (and the old state/references in eclipse are not valid).
Pressing refresh on all the involved project solves the problem (e.g. eclipse rebuilds them). (Running eclipse europa on jdk 1.6)

Wow - I was about to stress out when this started happening to me - found this issue as number one google hit for "eclipse maven class not found" and thankfully, the work around of:
"In the project containing your tests, edit Java Build Path | Order and Export: Make sure M2 Dependencies appears BEFORE JRE System Library." works!
How on earth did you figure out the work around???
I actually changed to order in the project my junits depended on, not the project which contained my tests! I didn't try it the other way around.

woah that's weird. ok, tried to try it the other way around, and after putting maven dependencies to last again, the problem didn't reoccur! even after a clean! hmmm...

Perhaps it's an eclipse bug?

I'm on 3.4.

ok, problems back and the work around didn't work this time.
I also have an issue with opening files with getResourceAsStream in the other problematic project and think it may be related...

I encountered the same problem. After some head banging, I changed the Eclipse classes folder to target\classes and did a Maven -> Update project configuration. It seems to work after this. Although, if you do a mvn clean, you must do a compile again to get this working.

Not sure about this, but perhaps Eclipse was compiling classes into 'bin' and was trying to find it in target\classes, causing the problem.

See http://blog.xemantic.com/2008/06/maven-integration-for-eclipse-and.html?widgetType=BlogArchive&widgetId=BlogArchive1&action=toggle&dir=close&toggle=YEARLY-1199142000000&toggleopen=MONTHLY-1220220000000

Thanks Diego,

This was a life saver. Because of your post, it only took me a couple seconds to solve.

Jeff

Still no luck for me. Running on STS 2.1 / Eclipse 3.4, I still get a classnotfound when running src/test/java/com/xxx/ActionTest.java which uses src/main/java/com/xxx/Action.java class. I tried to enble Marven Dependencies Management, update project configuration, still no luck. I disabled Dependencies Management, try again, no luck. Tried to put marven dependencies before JRE System Library. No luck again. I don't understand the problem. I have an other project that I receive from a training class, which work, but nothing seems to be different. I analyzed all parameters of the project, no huge difference.... Does anyone as another idea?

It seems you guys are reporting the issue at the wrong location. This JIRA project MECLIPSE is about the maven-eclipse-plugin, i.e. the thing that one invokes on the CLI like mvn eclipse:eclipse. However, you seem to have problems with M2Eclipse, this has its issue tracker at https://issues.sonatype.org/browse/MNGECLIPSE.

@Benjamin

You are wrong, with m2eclipse we can reslove this problem with Update project configuration. Without this plugin we cant using JUnit in maven!

Hi! Ive the same problem, but I solved that, rebuilding the index of the local repository!

Changing the build order dont make any effect for me!

Well, changing the order of Maven Dependencies and JRE System Library (1st and 2nd, respectively) did the trick for me.

I'm using Eclipse 3.6.2 (Helios), and m2eclipse 0.12.1.20110112-1712.