JUnit测试RestTemplate时Mock失效连接真实URL问题求助

你的测试代码Mock了RestTemplate但未生效，核心原因是业务类TestRestTemplate的RestTemplate是在自身构造函数中直接new出来的，测试类中@Mock的实例和业务类里的实例完全独立，Mock配置无法覆盖真实实例，代码依然会发起实际HTTP请求，导致连接超时。

以下两种方案均可解决问题，核心思路是让业务类的RestTemplate实例支持外部注入，测试时传入Mock对象。

方案1：构造函数注入RestTemplate #

修改业务类，通过构造函数传入RestTemplate，同时保留无参构造函数兼容原有运行方式：

public class TestRestTemplate {
    private final RestTemplate restTemplate;

    // 带参数构造函数，用于测试注入Mock实例
    public TestRestTemplate(RestTemplate restTemplate) {
        this.restTemplate = restTemplate;
    }

    // 无参构造函数，保持原有独立程序运行逻辑
    public TestRestTemplate() {
        this(new RestTemplate());
    }

    public void identifyInvoiceCategory(final Properties properties) throws Throwable {
        final ResponseEntity<SearchResponse> exchange = restTemplate.exchange(
                properties.getProperty("ENDPOINT"), HttpMethod.GET,
                new HttpEntity<>(createSearchRequest(), createHttpHeader()), SearchResponse.class);

        final SearchResponse searchResponse = exchange.getBody();
        searchResponse.getEndIndex();
    }

    private SearchRequest createSearchRequest() throws Throwable {
        final SearchRequest searchRequest = new SearchRequest();
        return searchRequest;
    }

    private HttpHeaders createHttpHeader() {
        HttpHeaders httpHeaders = new HttpHeaders();
        httpHeaders.setContentType(MediaType.APPLICATION_JSON);
        return httpHeaders;
    }
}

修改测试类，传入Mock的RestTemplate并构造有效响应（避免getBody()时NPE）：

@RunWith(MockitoJUnitRunner.class)
public class TestRest {
    @Mock
    private RestTemplate restTemplate;

    @Test
    public void testIdentifyInvoiceCategoryValid() throws Throwable {
        // 构造Mock响应数据
        SearchResponse mockResponse = new SearchResponse();
        mockResponse.setEndIndex(10); // 根据实际类的属性设置有效值
        ResponseEntity<SearchResponse> responseEntity = new ResponseEntity<>(mockResponse, HttpStatus.OK);

        // 配置Mock行为
        Mockito.when(restTemplate.exchange(
                ArgumentMatchers.anyString(), 
                ArgumentMatchers.eq(HttpMethod.GET),
                ArgumentMatchers.any(HttpEntity.class), 
                ArgumentMatchers.<Class<SearchResponse>>any())
        ).thenReturn(responseEntity);

        // 传入Mock实例创建业务类对象
        TestRestTemplate testInstance = new TestRestTemplate(restTemplate);
        testInstance.identifyInvoiceCategory(createProperties());
    }

    private Properties createProperties() {
        final Properties properties = new Properties();
        properties.setProperty("ENDPOINT", "http://www.test.com");
        return properties;
    }
}

方案2：Setter方法注入RestTemplate #

如果不想修改构造函数，可添加Setter方法实现注入：

业务类添加Setter：

public class TestRestTemplate {
    private RestTemplate restTemplate;

    public TestRestTemplate() {
        restTemplate = new RestTemplate();
    }

    // 添加Setter用于测试注入Mock实例
    public void setRestTemplate(RestTemplate restTemplate) {
        this.restTemplate = restTemplate;
    }

    // 其余业务方法不变...
}

测试类修改为通过Setter注入Mock：

@RunWith(MockitoJUnitRunner.class)
public class TestRest {
    @Mock
    private RestTemplate restTemplate;

    @Test
    public void testIdentifyInvoiceCategoryValid() throws Throwable {
        // 构造Mock响应数据
        SearchResponse mockResponse = new SearchResponse();
        mockResponse.setEndIndex(10);
        ResponseEntity<SearchResponse> responseEntity = new ResponseEntity<>(mockResponse, HttpStatus.OK);

        // 配置Mock行为
        Mockito.when(restTemplate.exchange(
                ArgumentMatchers.anyString(), 
                ArgumentMatchers.eq(HttpMethod.GET),
                ArgumentMatchers.any(HttpEntity.class), 
                ArgumentMatchers.<Class<SearchResponse>>any())
        ).thenReturn(responseEntity);

        TestRestTemplate testInstance = new TestRestTemplate();
        // 注入Mock实例
        testInstance.setRestTemplate(restTemplate);
        testInstance.identifyInvoiceCategory(createProperties());
    }

    private Properties createProperties() {
        final Properties properties = new Properties();
        properties.setProperty("ENDPOINT", "http://www.test.com");
        return properties;
    }
}

内容的提问来源于stack exchange，提问作者user1862354