如何使用PowerMock和Mockito对Java 11 HttpClient代码进行Mock

这段代码Mock的核心难点是HttpClient.newBuilder()、HttpRequest.newBuilder()都属于静态方法，普通Mockito无法直接Mock静态类/静态方法，必须结合PowerMock开启静态Mock能力，具体实现步骤如下：

前置依赖配置 #

• 确认使用兼容的PowerMock、Mockito版本组合，推荐适配版本：Mockito 2.28.x + PowerMock 2.0.x，避免版本冲突
• JUnit 4用户需要提前引入powermock-module-junit4、powermock-api-mockito2依赖

完整实现步骤 #

1. 测试类基础注解配置 #

@RunWith(PowerMockRunner.class)
// 将要Mock的静态类全量加入配置
@PrepareForTest({HttpClient.class, HttpRequest.class})
public class HttpClientMockTest {
    // 测试逻辑写在该类中
}

2. Mock HttpClient构建全流程 #

// 开启HttpClient静态方法Mock能力
PowerMockito.mockStatic(HttpClient.class);
// Mock HttpClient.Builder实例
HttpClient.Builder mockClientBuilder = Mockito.mock(HttpClient.Builder.class);
// 静态方法newBuilder被调用时返回我们自定义的Mock Builder
Mockito.when(HttpClient.newBuilder()).thenReturn(mockClientBuilder);

// 按Builder调用链依次配置返回值：authenticator -> connectTimeout -> build
Mockito.when(mockClientBuilder.authenticator(Mockito.any(Authenticator.class))).thenReturn(mockClientBuilder);
Mockito.when(mockClientBuilder.connectTimeout(Mockito.any(Duration.class))).thenReturn(mockClientBuilder);
// Mock最终生成的HttpClient实例，后续可基于该实例Mock send方法的返回值
HttpClient mockHttpClient = Mockito.mock(HttpClient.class);
Mockito.when(mockClientBuilder.build()).thenReturn(mockHttpClient);

3. Mock HttpRequest构建全流程 #

// 开启HttpRequest静态方法Mock能力
PowerMockito.mockStatic(HttpRequest.class);
// Mock HttpRequest.Builder实例
HttpRequest.Builder mockRequestBuilder = Mockito.mock(HttpRequest.Builder.class);
// 静态方法newBuilder被调用时返回我们自定义的Mock Builder
Mockito.when(HttpRequest.newBuilder()).thenReturn(mockRequestBuilder);

// 按Builder调用链依次配置返回值：POST -> uri -> build
Mockito.when(mockRequestBuilder.POST(Mockito.any(HttpRequest.BodyPublisher.class))).thenReturn(mockRequestBuilder);
Mockito.when(mockRequestBuilder.uri(Mockito.any(URI.class))).thenReturn(mockRequestBuilder);
// Mock最终生成的HttpRequest实例
HttpRequest mockRequest = Mockito.mock(HttpRequest.class);
Mockito.when(mockRequestBuilder.build()).thenReturn(mockRequest);

4. 可选参数校验 #

如果需要验证业务代码传入的配置是否符合预期，可增加如下校验逻辑：

// 验证authenticator传入的账号密码是否正确
Mockito.verify(mockClientBuilder).authenticator(Mockito.argThat(authenticator -> {
    PasswordAuthentication auth = authenticator.getPasswordAuthentication();
    return "abcd".equals(auth.getUserName()) && "efgh".equals(new String(auth.getPassword()));
}));
// 验证请求目标地址是否符合预期
Mockito.verify(mockRequestBuilder).uri(Mockito.eq(URI.create("www.xyz.com")));

如果你使用的是Mockito 3.4.0及以上版本，可以不需要引入PowerMock，直接用Mockito自带的静态Mock能力，调用Mockito.mockStatic(HttpClient.class)即可，其余逻辑和上述实现完全一致，不需要额外配置PowerMock相关注解。

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