如何通过Mockito模拟无法访问的第三方类属性

Question

I have this beautiful scenery in front of me including JSF, jUnit(4.11) and Mockito(1.10.19):

@ManagedBean
@ViewScoped
public class UserAuth implements Serializable {

 private List<UserRole> roleList;
 private LocalChangeBean localChangeBean;

public UserAuth() {

        roleList = new ArrayList<UserRole>();

        localChangeBean = (LocalChangeBean) FacesContext.getCurrentInstance().getExternalContext().getSessionMap().get("localChangeBean");

        setLocalChangeBean(localChangeBean);

        setRoleList(getLocalChangeBean().getRoleList());
        //many other property setting and some JSF stuff
    }

 public boolean checkAuth() {
        for (UserRole role : getRoleList()) {
            if(role.getName().equals("SUPER_USER"))
                return true;
        }
        return false;
    }
}

//A hell of a lot more code, proper getters/setters etc.

Here is the test class:

public class UserAuthTest {

    @Test
    public void testCheckAuth() {

        UserAuth bean = mock(UserAuth.class);

        List<UserRole> mockRoleList = new ArrayList<UserRole>();
        UserRole ur = mock(UserRole.class);
        when(ur.getName()).thenReturn("SUPER_USER");
        mockRoleList.add(ur);

        when(bean.getRoleList()).thenReturn(mockRoleList);

        assertEquals(true, bean.checkAuth());
    }

The thing is; UserRole class is not reachable by me, it's another part of the project. It doesn't have a no-argument constructor and the existing constructor requires other unreachable classes etc. Thus I can't instantiate it. In these circumstances, all I want to do is to make that mock UserRole object behave such as returning the needed String when it's getName() method gets called.

But obviously; when I try to add that UserRole mock object into the List of UserRoles, the behavior that I tried to define is not stored with the object. And yes, the code looks pretty funny in its current stance. Though I left it there to learn what should I do to achieve this simple, little goal of mine.

Post-Edit: I couldn't manage the problem without changing the original bean, though I followed Jeff's suggestion below and it worked well as a strategy of isolation. I did not mark it as the best answer since the question was "How to mock an unreachable third party class?" (in the current example its the UserRole class) Eventually the noob me understood that "Mocking an unreachable third party class is no different than mocking any other class".

Here is how I managed it:

@ManagedBean
@ViewScoped
public class UserAuth implements Serializable {

 private List<UserRole> roleList;
 private LocalChangeBean localChangeBean;

public UserAuth() {

        //the actual constructor including all JSF logic, highly dependent
    }

UserAuth(List<UserRole> roleList) {
    setRoleList(roleList);
    //package private test-helper constructor which has no dependency on FacesContext etc.
  }
 public boolean checkAuth() {
        for (UserRole role : getRoleList()) {
            if(role.getName().equals("SUPER_USER"))
                return true;
        }
        return false;
    }
}

And here is the test class (attention to the iterator mock, it has the whole trick):

public class UserAuthTest {

private UserRole mockRole;
private Iterator<UserRole> roleIterator;
private List<UserRole> mockRoleList;

private UserAuth tester; 

@SuppressWarnings("unchecked")
@Before
public void setup() {

    mockRoleList = mock(List.class);
    mockRole = mock(UserRole.class);
    roleIterator = mock(Iterator.class);

    when(mockRoleList.iterator()).thenReturn(roleIterator);
    when(roleIterator.hasNext()).thenReturn(true, false);
    when(roleIterator.next()).thenReturn(mockRole);

    tester = new UserAuth(mockRoleList);

}

@Test
public void testCheckAuth(){
    when(mockRole.getName()).thenReturn("SUPER_USER");
    assertEquals("SUPER_USER expected: ", true, tester.checkAuth());
}

Answer 1

You don't need Mockito. A quick refactor will do this for you.

Your problem: Your code relies on a static call to FacesContext.getCurrentInstance() in your constructor, that is difficult to prepare or substitute out in tests.

Your proposed solution: Use Mockito to substitute out the FacesContext instance, the external context, or the session map. This is partly tricky because Mockito works by proxying out the instances, so without PowerMock you won't be able to replace the static call, and without a way to insert the mock into FacesContext or its tree, you have no alternative.

My proposed solution: Break out the bad call FacesContext.getCurrentInstance().getExternalContext.getSessionMap() into the default constructor. Don't call that constructor from tests; assume it works in the unit testing case. Instead, write a constructor that takes in the session map as a Map<String, Object> , and call that constructor from your tests. That gives you the best ability to test your own logic.

@ManagedBean
@ViewScoped
public class UserAuth implements Serializable {
  // [snip]
  public UserAuth() {
    // For the public default constructor, use Faces and delegate to the
    // package-private constructor.
    this(FacesContext.getCurrentInstance().getExternalContext().getSessionMap());
  }

  /** Visible for testing. Allows passing in an arbitrary map. */
  UserAuth(Map<String, Object> sessionMap) {
    roleList = new ArrayList<UserRole>();

    localChangeBean = (LocalChangeBean) sessionMap.get("localChangeBean");

    setLocalChangeBean(localChangeBean);
    setRoleList(getLocalChangeBean().getRoleList());
    // [snip]
  }
}

ps Another solution is to actually get the session map within the test and insert the value you need, but you have to be careful there not to pollute your other tests by installing something into a static instance that may persist between tests.