How to mock object which create within the test method?

Question

I have ContextListener which inject in ServletContext object for work with database. And this DBJoint object create in method which test:

@WebListener
public class ContextListener implements ServletContextListener {

    @Override
    public void contextInitialized(ServletContextEvent servletContextEvent) {

        final ServletContext servletContext =
                servletContextEvent.getServletContext();

        final DBJoint joint = new DBJointHandler(
                "database_scripts", "authentication_database");

        servletContext.setAttribute("db", joint);
    }
}

For testing servletContext.setAttribute("db", joint); I need DBJoint joint for send in setAttribute.

My test:

@Test
public void whenThen() {

    final ServletContextEvent event = mock(ServletContextEvent.class);
    final ServletContext context = mock(ServletContext.class);
    when(event.getServletContext()).thenReturn(context);

    final ContextListener listener = new ContextListener();
    listener.contextInitialized(event);
    DBJoint joint = ..?// how to mocking this?
    verify(context).setAttribute("db", joint);
}

1. Testing for servletContext.setAttribute("db", joint); is possibly?
2. If answer "yes", how.

Thank You.

Answer 1

First you need to understand that your servletContext object is a mocked object and not a real object. The joint object is real and you don't need to mock. You can possibly test servletContext.setAttribute("db", joint); using mockito verify

verify(servletContext).setAttribute(eq("db"), any(DBJoint.class));

Answer 2

You can mock constructor by using power mock. Try this

DBJointHandler joint = new DBJointHandler("database_scripts", "authentication_database"); try { PowerMockito.whenNew(DBJointHandler.class).withArguments("database_scripts", "authentication_database").thenReturn(joint); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); }