Yes you can. Just get the Application instance from the FacesContext:
Application application = jsfServerSession.getFacesContext().getApplication();
Then use one of the createComponent() methods on the Application instance.
if you have any example with you right now ..can you send it to me...it would be helpful for me
If you want to write pure unit tests, build JSFUnit  and take a look at org.jboss.jsfunit.stub . This is a port of the Shale test framework . The package name "mock" was changed to "stub" because mocks aren't stubs . Enjoy.
if you say to get the Application instance ..then we need to have ServerSession and ClientSession ...i am asking at the component level..means if i have created a custom component and before rendering that on to a jsf page if i need to test it ..is it possible in jsfunit
If you are talking about testing outside of the servlet container then you can use the code Dennis Byrne was talking about. Dennis is working on the mock/stub library that allows you to test components outside of a running container. I'm sure he'd love to have your feedback if you want to give it a try.