JUnit  Basic concepts needed

I am not familiar with JUnit . I was reading a Spring tutorial where I found they used JUnit in the tutorial  . So i need little Junit help to pass over that section and get going on the spring tutorial.

tutorial :
http://static.springsource.org/docs/Spring-MVC-step-by-step/part1.html#step1.9
 
see section  :   1.9. Write a test for the Controller

.Q1) I am surprised to see that they did not deploy the HelloController   in the server but tested the view  using JUnit !  ...thats interesting......but suppose instead of  HelloController  , if we had a HttpServlet ..can we still be able to test  without deploying the Httpservlet  in the server ?? I am asking because  Httpservlet  lives  inside the server ....So can we test a  Httpservlet without deploying it in the server using JUnit ?

Q2)
ModelAndView modelAndView = controller.handleRequest(null, null);      

why null,null ?  

Q3)
assertEquals("hello.jsp", modelAndView.getViewName());

modelAndView.getViewName());  
// how this can work upon ? controller is not yet deployed ..it cant respond....can it ??


Q4)
See the run output ...need to uderstand this
tests:
    [junit] Running springapp.web.HelloWorldControllerTests
    [junit] Oct 30, 2007 11:31:43 PM springapp.web.HelloController handleRequest
    [junit] INFO: Returning hello view
    [junit] Tests run: 1, Failures: 0, Errors: 0, Time elapsed: 0.03 sec
    [junit] Testsuite: springapp.web.HelloWorldControllerTests
    [junit] Tests run: 1, Failures: 0, Errors: 0, Time elapsed: 0.03 sec  //  WHY  TWICE PRINT ??

    [junit] ------------- Standard Error -----------------
    [junit] Oct 30, 2007 11:31:43 PM springapp.web.HelloController handleRequest
    [junit] INFO: Returning hello view // THIS IS NOT ERROR .WHY THIS IS UNDER  StandardError?
    [junit] ------------- ---------------- ---------------

Can you explain this run output ? I see there is some output  under  Standard Error  ...but that is not error ......and also "Tests run: 1" has been printed twice ....why ? does JUnit execute twice the test case to print two times ?


Q5) what it checks
assertNotNull(modelAndView.getModel());

looks like a null object checking ...if  it finds null ..does that going to throw some error under Standard Error  ??