如何模拟客户端或服务器错误的RestTemplate？

RestTemplate restTemplate = new RestTemplate();
MockRestServiceServer mockServer = MockRestServiceServer.createServer(restTemplate);

// 模拟客户端错误，返回400 Bad Request
mockServer.expect(requestTo("/api/endpoint"))
    .andExpect(method(HttpMethod.GET))
    .andRespond(withBadRequest());

// 发送HTTP请求
ResponseEntity<String> response = restTemplate.getForEntity("/api/endpoint", String.class);
assertEquals(HttpStatus.BAD_REQUEST, response.getStatusCode());

RestTemplate restTemplate = new RestTemplate();
MockRestServiceServer mockServer = MockRestServiceServer.createServer(restTemplate);

// 模拟服务器错误，返回500 Internal Server Error
mockServer.expect(requestTo("/api/endpoint"))
    .andExpect(method(HttpMethod.GET))
    .andRespond(withServerError());

// 发送HTTP请求
ResponseEntity<String> response = restTemplate.getForEntity("/api/endpoint", String.class);
assertEquals(HttpStatus.INTERNAL_SERVER_ERROR, response.getStatusCode());