Usage of Hamcrest instanceOf

LoginTest.java

    public void testLogin() throws Exception {
        this.mockMvc.perform((post("/login").accept(MediaType.ALL).param("id", "admin").param("password", "admin").with(csrf())))
                .andDo(print())
                .andExpect(status().is3xxRedirection())
                .andExpect(request().sessionAttribute("SPRING_SECURITY_LAST_EXCEPTION", instanceOf(BadCredentialsException.class)));
    }