如何编写静态无效方法的单元测试

Question

我遇到了一个问题，我不知道如何编写 static void 方法的单元测试。

我现在有一个使用 Apache HttpClient 的 HttpHelper class。代码如下。

public class HttpHelper {
    private static CloseableHttpClient httpClient;

    public static void init() {
        httpClient = HttpClients.custom().setSSLContext(getDummySSL()).build();
    }

    public static void closeHttpClient() throws IOException {
        httpClient.close();
    }

    private static SSLContext getDummySSL() {
        ...omit
    }

    private static void send() {
        HttpGet httpGet = new HttpGet("https://someUrl.com");

        try(CloseableHttpResponse httpResponse = httpClient.execute(httpGet)) {
            if(httpResponse.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
                responseString = EntityUtils.toString(httpResponse.getEntity());
                // do something
            } else {
                throw new Exception();
            }
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

所以在我的主程序中，我将调用 HttpHelper.init() 来初始化 httpClient。每次我想发送请求时，我都会调用 HttpHelper.send()。因为我不想每次都创建一个新的 httpClient 。最后，我会调用 HttpHelper.close() 关闭 httpClient。

我想知道如何测试那些 void 方法。我的想法是在我的测试中创建一个 CloseableHttpClient，然后调用 HttpHelper.init() 来创建实际的。然后比较我预期的和实际的是一样的。我说得对吗？

由于变量和方法被声明为静态的。编写单元测试有点困难。有很多帖子说使方法静态化是一种不好的做法。但是在我的示例中，我不知道如何避免将它们声明为静态并保留单个 CloseableHttpClient 实例。

谢谢！

Answer 1

单实例保证主要是用单例模式解决的。单元测试的一个常见技巧是创建一个具有受保护可见性的构造函数，您可以在其中放置参数进行测试。 class 终于可以变成这个样子了。

public class HttpHelper {
    private static HttpHelper INSTANCE = new HttpHelper();

    public static HttpHelper getInstance() {
        return INSTANCE;
    }


    private CloseableHttpClient httpClient;

    private HttpHelper() {
        SSLContext sslContext = getDummySSL();
        this(HttpClients.custom().setSSLContext(sslContext).build(), sslContext);
    }

    protected HttpHelper(CloseableHttpClient httpClient, SSLContext sslContext) {
        this.httpClient = httpClient;
    }

    public void closeHttpClient() throws IOException {
        httpClient.close();
    }

    private static SSLContext getDummySSL() {
        ...
    }

    private void send() {
        ...
    }
}

我也会将 getDummySSL 重命名为 createDummySSL 但这是细节。

Answer 2

class 如此静态是不好的，因为很难对其进行测试。我理解您为什么想要这个，但您可以获得与此相同的所有好处：

public class HttpHelper {

    private static HttpHelper DEFAULT_INSTANCE = null;

    private CloseableHttpClient httpClient;

    public HttpHelper(CloseableHttpClient httpClient) {
        this.httpClient = httpClient;
    }

    public static void getDeafultInstance() { // this should probably be synchronised for thread safety
        if (DEFAULT_INSTANCE == null) {
            DEFAULT_INSTANCE = httpClient = HttpClients.custom().setSSLContext(getDummySSL()).build();
        }
        return DEAFULT_INSTANCE;
    }

    private static SSLContext getDummySSL() {
        ...omit
    }

    public void closeHttpClient() throws IOException {
        httpClient.close();
    }

    private void send() {
        HttpGet httpGet = new HttpGet("https://someUrl.com");

        try(CloseableHttpResponse httpResponse = httpClient.execute(httpGet)) {
            if(httpResponse.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
                responseString = EntityUtils.toString(httpResponse.getEntity());
                // do something
            } else {
                throw new Exception();
            }
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

然后你可以像这样对其进行单元测试:


public class HttpHelperTest {

    @Test
    public testSendsRequestToSomeUrl() {
        CloseableHttpClient httpClientMock = mock();
        when(httpClient.execute(any())).thenReturn(..http_response_where_stauts_code_is_ok..)
        HttpHelper httpHelper = new HttpHelper(httpClientMock)
        httpHelper.send()
        verify(httpClient).execute(new HttpGet("https://someUrl.com"))
    }

}

并像这样在实际代码中使用它：

HttpHelper.getDeafultInstance().send()

P.S.

如果你有某种可用的依赖注入框架，那么你完全可以摆脱静态方法。

如何编写静态无效方法的单元测试

How to write unit test of a static void method

java

unit-testing

httpclient

mockito

junit5