How to test JSF bean methods that use session parameters?

Question

I'm having a hard time trying to implement unit tests on my JSF backing bean classes... For instance some of the methods use session or request parameters, obtained using this sort of code:

FacesContext.getCurrentInstance().getExternalContext().getSessionMap().get("paramKey");.

My question is: how can I test a method which obtains values from the session or request?

Answer 1

What I usually do is to avoid calling static methods into the beans I want to test. That implies your current code to be refactored:

FacesContext.getCurrentInstance().getExternalContext()
    .getSessionMap().get("paramKey");

Are there ways to test them with their static method calls? Probably there are, but they led me to a lot of trouble more than help. So at the end I got rid of them and changed my design. Just let a second bean do it (which you'll mock later). In your case, create a @SessionScoped bean which manages that functionality:

@ManagedBean
@SessionScoped
public class SessionBean{

    public Object getSessionParam(String paramKey){
        FacesContext.getCurrentInstance().getExternalContext()
           .getSessionMap().get(paramKey);
    }

}

And inject that bean in every single bean that needs it (I usually extend my view/request beans from an abstract bean which has it, so don't have to implement it in every single bean):

@ManagedBean
@RequestScoped
public class RequestBean{

    @ManagedProperty(value="#{sessionBean}")
    private SessionBean sessionBean;

    public void accessSessionParam(){
        sessionBean.getSessionParam("name");
    }

}

That way you can access static methods easily, via your auxiliary SessionBean. Then, how to test it? Just create a mock of it (using Mockito, for instance):

public class Test{

    public void test1(){
        SessionBean sb = Mockito.mock(SessionBean.class);
        //Mock your 'getSessionParam' method
        ValueBean vb = new ValueBean();
        Mockito.when(sb.getSessionParam(Mockito.anyString()).thenReturn(vb);
        //Create your bean to test and set your mock to it
        RequestBean rb = new RequestBean();
        rb.setSessionBean(sb);
        //here you can test your RequestBean assuming 
        //sessionBean.getSessionParam() 
        //will return vb for every single call
    }

}

Answer 2

It is possible to mock FacesContext but this is less than ideal. Mockito example:

import javax.faces.context.FacesContext;
import org.mockito.Mockito;
import org.mockito.invocation.InvocationOnMock;
import org.mockito.stubbing.Answer;

public abstract class ContextMocker extends FacesContext {
  private ContextMocker() {}

  private static final Release RELEASE = new Release();

  private static class Release implements Answer<Void> {
    @Override
    public Void answer(InvocationOnMock invocation) throws Throwable {
      setCurrentInstance(null);
      return null;
    }
  }

  public static FacesContext mockFacesContext() {
    FacesContext context = Mockito.mock(FacesContext.class);
    setCurrentInstance(context);
    Mockito.doAnswer(RELEASE)
        .when(context)
        .release();
    return context;
  }
}

If your platform supports it, prefer CDI to JSF managed beans. CDI has static dependency checking and injects proxies to prevent scope leak. CDI doesn't support all of JSF's features but it is relatively easy to connect JSF managed beans to CDI where necessary.

JSF managed beans restrict the scope that you inject types into but even that can lead to scope leaks. For example, the #{sessionScope} variable can be injected into a session scope bean even though the object belongs to the request scoped ExternalContext. It is possible to overcome this by writing your own JSF bean proxies.

Note: most of this was written with Java EE 6 in mind; things might have improved with Java EE 7.