使用 Android volley 进行单元测试

Question

我想知道如何为 volley 框架创建单元测试。模拟请求和响应，以便我可以创建不需要 Web 服务工作和网络访问的单元测试。

我用谷歌搜索了它，但我根本找不到关于框架的太多信息

Answer 1

我实现了一个名为 FakeHttpStack 的 HttpStack 子类，它从 res/raw 中的本地文件加载假响应正文。我这样做是为了开发目的，也就是说，我可以在服务器准备好之前为新 API 开发一些东西，但是你可以从这里学到一些东西（例如，覆盖 HttpStack#peformRequest 和 createEntity）。

/**
 * Fake {@link HttpStack} that returns the fake content using resource file in res/raw.
 */
class FakeHttpStack implements HttpStack {
    private static final String DEFAULT_STRING_RESPONSE = "Hello";
    private static final String DEFAULT_JSON_RESPONSE = " {\"a\":1,\"b\":2,\"c\":3}";
    private static final String URL_PREFIX = "http://example.com/";
    private static final String LOGGER_TAG = "STACK_OVER_FLOW";

    private static final int SIMULATED_DELAY_MS = 500;
    private final Context context;

    FakeHttpStack(Context context) {
        this.context = context;
    }

    @Override
    public HttpResponse performRequest(Request<?> request, Map<String, String> stringStringMap)
            throws IOException, AuthFailureError {
        try {
            Thread.sleep(SIMULATED_DELAY_MS);
        } catch (InterruptedException e) {
        }
        HttpResponse response
                = new BasicHttpResponse(new BasicStatusLine(HttpVersion.HTTP_1_1, 200, "OK"));
        List<Header> headers = defaultHeaders();
        response.setHeaders(headers.toArray(new Header[0]));
        response.setLocale(Locale.JAPAN);
        response.setEntity(createEntity(request));
        return response;
    }

    private List<Header> defaultHeaders() {
        DateFormat dateFormat = new SimpleDateFormat("EEE, dd mmm yyyy HH:mm:ss zzz");
        return Lists.<Header>newArrayList(
                new BasicHeader("Date", dateFormat.format(new Date())),
                new BasicHeader("Server",
                        /* Data below is header info of my server */
                        "Apache/1.3.42 (Unix) mod_ssl/2.8.31 OpenSSL/0.9.8e")
        );
    }

    /**
     * returns the fake content using resource file in res/raw. fake_res_foo.txt is used for
     * request to http://example.com/foo
     */
    private HttpEntity createEntity(Request request) throws UnsupportedEncodingException {
        String resourceName = constructFakeResponseFileName(request);
        int resourceId = context.getResources().getIdentifier(
                resourceName, "raw", context.getApplicationContext().getPackageName());
        if (resourceId == 0) {
            Log.w(LOGGER_TAG, "No fake file named " + resourceName
                    + " found. default fake response should be used.");
        } else {
            InputStream stream = context.getResources().openRawResource(resourceId);
            try {
                String string = CharStreams.toString(new InputStreamReader(stream, Charsets.UTF_8));
                return new StringEntity(string);
            } catch (IOException e) {
                Log.e(LOGGER_TAG, "error reading " + resourceName, e);
            }
        }

        // Return default value since no fake file exists for given URL.
        if (request instanceof StringRequest) {
            return new StringEntity(DEFAULT_STRING_RESPONSE);
        }
        return new StringEntity(DEFAULT_JSON_RESPONSE);
    }

    /**
     * Map request URL to fake file name
     */
    private String constructFakeResponseFileName(Request request) {
        String reqUrl = request.getUrl();
        String apiName = reqUrl.substring(URL_PREFIX.length());
        return "fake_res_" + apiName;
    }
}

要使用 FakeHttpStack，您只需将它传递给您的 RequestQueue。我也覆盖了 RequestQueue。

public class FakeRequestQueue extends RequestQueue {
    public FakeRequestQueue(Context context) {
        super(new NoCache(), new BasicNetwork(new FakeHttpStack(context)));
    }
}

这种方法的好处在于，它不需要对您的代码进行太多更改。您只需在测试时将您的 RequestQueue 切换为 FakeRequestQueue。因此，它可以用于验收测试或系统测试。

另一方面，对于单元测试，可能有更紧凑的方式。例如，您可以将 Request.Listener 子类实现为单独的类，以便可以轻松测试 onResponse 方法。我建议您详细说明您要测试的内容或放置一些代码片段。

Answer 2

查看 volley tests 文件夹，您可以在其中找到示例。

MockCache.java
MockHttpClient.java
MockHttpStack.java
MockHttpURLConnection.java
MockNetwork.java
MockRequest.java
MockResponseDelivery.java

Answer 3

不是 100% 确定我理解您想要做什么，但如果我理解了，那么 easymock（一个允许创建模拟类的库，您可以调用并接收预定的响应）将帮助您解决很多。一个叫 Lars Vogel 的人有一篇关于这个主题的不错的文章，我在不久前使用它时发现它很有用。

http://www.vogella.com/articles/EasyMock/article.html

Answer 4

这是@Dmytro 提到的the current volley's MockHttpStack 的副本

package com.android.volley.mock;
import com.android.volley.AuthFailureError;
import com.android.volley.Request;
import com.android.volley.toolbox.HttpStack;
import org.apache.http.HttpResponse;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
public class MockHttpStack implements HttpStack {
    private HttpResponse mResponseToReturn;
    private IOException mExceptionToThrow;
    private String mLastUrl;
    private Map<String, String> mLastHeaders;
    private byte[] mLastPostBody;
    public String getLastUrl() {
        return mLastUrl;
    }
    public Map<String, String> getLastHeaders() {
        return mLastHeaders;
    }
    public byte[] getLastPostBody() {
        return mLastPostBody;
    }
    public void setResponseToReturn(HttpResponse response) {
        mResponseToReturn = response;
    }
    public void setExceptionToThrow(IOException exception) {
        mExceptionToThrow = exception;
    }
    @Override
    public HttpResponse performRequest(Request<?> request, Map<String, String> additionalHeaders)
            throws IOException, AuthFailureError {
        if (mExceptionToThrow != null) {
            throw mExceptionToThrow;
        }
        mLastUrl = request.getUrl();
        mLastHeaders = new HashMap<String, String>();
        if (request.getHeaders() != null) {
            mLastHeaders.putAll(request.getHeaders());
        }
        if (additionalHeaders != null) {
            mLastHeaders.putAll(additionalHeaders);
        }
        try {
            mLastPostBody = request.getBody();
        } catch (AuthFailureError e) {
            mLastPostBody = null;
        }
        return mResponseToReturn;
    }
}