Getting test "Unresolved compilation problems" errors with JUnit but there are no problems in code

When running JUnit tests i am getting "Unresolved compilation problems" errors. But these are not compilation errors. Eclipse is not reporting any issues in the "problems" tab.

And this is happening on another Eclipse environment. on a mac. I think the JUnit is running the tests and it is not finding classes that are in other packages. Some yes, some no. I tried to add to the "Run Configuration" of the JUnit as projects, folders or jars. Nothing else. What can this be? All the errors under the Unresolved Compilation problems are "cannot resolve type, etc". Thanks, Roy