If you try to load the javax.persistence.EntityManager class coming from standard java.net Repository you will get the following Exception:

java.lang.ClassFormatError: Absent Code attribute in method that is not native or abstract in class file javax/persistence/LockModeType
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClassCond(ClassLoader.java:632)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:616)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
        at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:190)

Loading a class is needed for mocking, so the following code will not run:

@Stateless
public class EJB3WithEntityManager {
    @PersistenceContext
    EntityManager em;
    
    public void save(AnEntity ae){
        em.persist(ae);
    }
}

public class EJB3WithEntityManagerTest {
    private EJB3WithEntityManager cut;
    @Before
    public void injectEntityManager(){
        this.cut = new EJB3WithEntityManager();
        this.cut.em = mock(EntityManager.class);
    }
    @Test
    public void testSomeMethod() {
        AnEntity ae = new AnEntity();
        this.cut.save(ae);
        verify(this.cut.em,times(1)).persist(ae);
    }
}

Instead of using

<dependency>
    <groupId>javax</groupId>
    <artifactId>javaee-web-api</artifactId>
    <version>6.0</version>
    <scope>provided</scope>
</dependency>

You should use alternative (geronimo, jboss etc.) dependencies:

<dependency>
       <groupId>org.apache.geronimo.specs</groupId>
       <artifactId>geronimo-ejb_3.1_spec</artifactId>
       <version>1.0</version>
       <scope>provided</scope>
   </dependency>
   <dependency>
       <groupId>org.apache.geronimo.specs</groupId>
       <artifactId>geronimo-jpa_2.0_spec</artifactId>
       <version>1.0</version>
       <scope>provided</scope>
   </dependency>

I cannot imagine any reasonable motivation behind removing the implementation of API-classes before uploading them into central maven repository, except political or licensing issues. This approach, however, has one advantage. You can tell whether a project is actually unit tested, or not, just by looking at the POM :-).

The whole example with workaround was checked into http://kenai.com/projects/javaee-patterns The name of the project is: MavenUnitTestWithCrippledAPI.

From http://www.adam-bien.com/roller/abien/entry/trouble_with_crippled_java_ee