Mocking classes in Eclipse Plug-in Tests

Mocking classes in Eclipse plug-ins requires some extra work (mocking interfaces works out of the box). 
Typically, an Eclipse application consists of several source plug-ins. The unit tests of these plug-ins 
are also stored in different plug-ins. E.g., if the main code of an application is stored in com.foo.core 
then the tests are stored in the plug-in com.foo.core.tests. 

Within Eclipse you have the possibility to start your tests as JUnit test or plug-in tests. For Junit tests 
Eclipse simply calls the JUnit runner, tests your class and reports the results. You can use jMock as 
a library on your classpath without any additional configuration. 

However, when running tests as plug-in tests Eclipse starts the target Eclipse platform, deploys your tests 
in this platform and starts these tests. Eclipse loads each plug-in with its OSGI classloader mechanism 
(http://www.eclipsezone.com/articles/eclipse-vms/): i.e., each plug-in will be loaded by an individual 
classloader. In this case you cannot create mocks for classes that are part of another plug-in out of the box. 
Since the classes to mock are loaded by a different classloader jMock cannot access them (actually cglib 
does not see these classes). 

In order to mock classes in other plug-ins you need to use the Eclipse buddy declarations in your plug-ins. 
Basically, you need to add in the MANIFEST of the plug-ins that contain the actual classes the following statement:
Eclipse-BuddyPolicy: registered. This statement instructs the Eclipse class loader to let other plug-ins access 
these classes. In your jMock test plug-in you need to add in the MANIFEST file the counterpart statement:
Eclipse-RegisterBuddy: com.foo.plugin1, com.foo.plugin2. Now you can mock classes of the plug-ins com.foo.plugin1
and com.foo.plugin2 in your test cases.


Example MANIFEST of plug-in jmock.example
-----------------------------------------
Manifest-Version: 1.0
Bundle-ManifestVersion: 2
Bundle-Name: Example Plug-in
Bundle-SymbolicName: jmock.example
Bundle-Version: 1.0.0
Bundle-Activator: jmock.example.Activator
Require-Bundle: org.eclipse.core.runtime
Eclipse-LazyStart: true
Export-Package: jmock.example
Eclipse-BuddyPolicy: registered

Example MANIFEST of plug-in jmock.example.tests
-----------------------------------------------
Manifest-Version: 1.0
Bundle-ManifestVersion: 2
Bundle-Name: Tests Plug-in
Bundle-SymbolicName: jmock.example.tests
Bundle-Version: 1.0.0
Bundle-Activator: jmock.example.tests.Activator
Require-Bundle: org.eclipse.core.runtime,
 org.junit,
 jmock.example
Eclipse-LazyStart: true
Eclipse-RegisterBuddy: jmock.example
Bundle-ClassPath: .,
 lib/cglib-2.1_3-src.jar,
 lib/cglib-nodep-2.1_3.jar,
 lib/hamcrest-api-1.0.jar,
 lib/hamcrest-library-1.0.jar,
 lib/jmock-2.1.0.jar,
 lib/jmock-junit3-2.1.0.jar,
 lib/jmock-legacy-2.1.0.jar,
 lib/objenesis-1.0.jar