Preventing System.exit()

You can prevent System.exit() by setting the appropriate thing in the SecurityManager. Try something like this in your JUnit test:

public void setUp() {
    System.setSecurityManager(new CatchSystemExit());
}
public void tearDown() {
    System.setSecurityManager(null);
}
private static class CatchSystemExit extends SecurityManager {
    /** @see SecurityManager */
    public void checkExit(int status) {
        m_exitCode = status;
        throw new SecurityException("System.exit() attempt caught");
    }
    /** @see SecurityManager */
    public void checkPermission(Permission perm, Object context) {
    }
    /** @see SecurityManager */
    public void checkPermission(Permission perm) {
    }
}