Per a comment on Glen Smith's blog (http://blogs.bytecode.com.au/glen/2008/03/12/mockfor-march---unit-testing-grails-controllers.html): I think we should have a new ControllerTestCase that has a method like def withMockController(Class c, Closure c) that does all of the setting up of params/flash/etc. Then you could just do withMockController(LoginController) { def controller = new LoginController() lc.login(goodUser) assertEquals "glen", session.account.userId assertEquals "/demo/", redirectParams.uri assertNull flash.loginError LoginCommand badUser = new LoginCommand(userId: 'glen', password: 'unlucky') lc.login(badUser) assertNull session.account assertNotNull flash.loginError } Thoughts? JIRA issue?