如何模拟 HttpClientBuilder 进行单元测试

Question

我正在尝试为 http post 实现编写一个单元测试。但是，我无法正确模拟 httpclient，并且我的 when 语句永远不会被触发。我编写的单元测试是进行实际的 http 调用，而不是使用模拟响应进行响应。我们如何继续模拟 HttpClientBuilder 创建的客户端？

Http方法实现：

HttpResponse postRequest(String url, String request) {

    HttpResponse resp = null;

    try {

        HttpClient client = HttpClientBuilder.create().useSystemProperties().build();

        HttpPost post = new HttpPost(url);

        post.addHeader("Content-Type", "application/x-www-form-urlencoded");

        post.setEntity(new StringEntity(request));

        resp = client.execute(post);

    } catch (Exception e) {

        return null;

    }

}

测试方法：

@Mock

private HttpClient httpClient;

when(httpClient.execute(any())).thenReturn(httpResponse);

Answer 1

我们如何继续模拟 HttpClientBuilder 创建的客户端？我们不！尽量避免嘲笑第三方的担忧创建紧密耦合的静态实现问题的抽象public interface HttpClientFactory {    public HttpClient create();}通过一个将在生产中使用的简单实现。public class HttpClientFactoryImpl implements HttpClientFactory {    //...    public HttpClient create() {        return HttpClientBuilder.create().useSystemProperties().build();    }    //...}使用依赖倒置，封装类应该显式依赖于抽象，以避免违反单一职责原则（SRP）public class SystemUnderTest {    private HttpClientFactory httpClientFactory;    public SystemUnderTest(HttpClientFactory httpClientFactory) {        this.httpClientFactory = httpClientFactory;    }    HttpResponse postRequest(String url, String request) {        HttpResponse resp = null;        try {            HttpClient client = httpClientFactory.create();            HttpPost post = new HttpPost(url);            post.addHeader("Content-Type", "application/x-www-form-urlencoded");            post.setEntity(new StringEntity(request));            resp = client.execute(post);            return resp;        } catch (Exception e) {            return null;        }    }}这种关注点分离 (SoC) 使其（您的封装类）能够更灵活地进行单独的单元测试。@Testpublic void testPostRequest() throws Exception {    // Arrange    HttpResponse expected = mock(HttpResponse.class);    HttpClient httpClient = mock(HttpClient.class);    when(httpClient.execute(any())).thenReturn(expected);    HttpClientFactory httpClientFactory = mock(HttpClientFactory.class);    when(httpClientFactory.create()).thenReturn(httpClient);    SystemUnderTest systemUnderTest = new SystemUnderTest(httpClientFactory);    String url = "http://url_here";    String request = "Hello World";    // Act    HttpResponse actual = systemUnderTest.postRequest(url, request);    // Assert    assertEquals(expected, actual);    //should also verify that the expected arguments as passed to execute()}