Mock mockContainer = new Mock(Container.class);
mockContainer.matchAndReturn("getInstance", C.args(C.eq(ContentTypeHandler.class), C.eq("x-www-form-urlencoded")), mockHandlerForm.proxy());
mockContainer.matchAndReturn("getInstance", C.args(C.eq(ContentTypeHandler.class), C.eq("json")), mockHandlerJson.proxy());
mockContainer.matchAndReturn("getInstance", C.args(C.eq(String.class), C.eq("struts.rest.handlerOverride.json")), null);
mockContainer.expectAndReturn("getInstanceNames", C.args(C.eq(ContentTypeHandler.class)), new HashSet(Arrays.asList("x-www-form-urlencoded", "json")));
mockRequest.setContentType(FormUrlEncodedHandler.CONTENT_TYPE);
mockRequest.setContent("a=1&b=2".getBytes("UTF-8"));
mgr.setContainer((Container) mockContainer.proxy());
ContentTypeHandler handler = mgr.getHandlerForRequest(mockRequest);