    public void preflightCheck() {
        String origin = "http://bla.com";
        String headers ="X-Data: Test";
        expect(backend.isCorsAccessAllowed(origin)).andReturn(true);
        replay(backend);

        Map<String,String> ret =  handler.handleCorsPreflightRequest(origin, headers);
        assertEquals(ret.get("Access-Control-Allow-Origin"),origin);
    }