|
目前的Android单元测试,很多都基于Roboletric框架,回避了Instrumentation test必须启动虚拟机或者真机的麻烦,执行效率大大提高。这里不讨论测试框架的选择问题,网络上有很多关于此类的资料。同时,现在几乎所有的App都会进行网络数据通信,Retrofit2就是其中非常方便的一个网络框架,遵循Restful接口设计。如此,再进行Android单元测试时,就必然需要绕过Retrofit的真实网络请求,mock出不同的response来进行本地逻辑测试。
retrofit官方出过单元测试的方法和介绍,详见参考文献4,介绍的非常细致。但是该方法是基于Instrumentation的,如果基于Robolectric框架,对于异步的请求就会出现问题,在stackoverflow上面有关于异步问题的描述,也给出了一个解决方法,但是需要对源码进行改动,所以不完美。本文将针对Robolectric+Retrofit2的单元测试过程中异步问题如何解决,提出一种更完美的解决方法。有理解不当的,后者更好的方案,欢迎大家提出指正。
一般使用retrofit2的时候,会出现一下代码片段 public void testMethod() {
OkHttpClient client = new OkHttpClient();
Retrofit retrofit = new Retrofit.Builder()
.baseUrl(BASE_URL)
.addConverterFactory(JacksonConverterFactory.create())
.client(client)
.build();
service = retrofit.create(xxxService.class);
Call<xxxService> call = service.getxxx();
call.enqueue(new Callback<xxx>() {
@Override
public void onResponse(Call<xxx> call, Response<xxxResponse> response) {
// Deal with the successful case
}
@Override
public void onFailure(Call<xxxResponse> call, Throwable t) {
// Deal with the failure case
}
});
} |
单元测试会测试testMethod方法,触发后根据不同的response,校验对应的逻辑处理,如上面的“// Deal with the successful case” 和 “// Deal with the failure case”。为了达到这个目的,需要实现一下两点:1)当触发该方法时,不会走真实的网络;2)可以mock不同的response进行测试
第一点可以借助MockWebServer来实现,具体的实现方法可以参考文献4,这里不展开了,重点看下第二点。在文献4中的sample#1,通过一个json文件,清晰简单的表明了测试的目的,所以我们也希望用这种方式。但是当实现后测试却发现,上面赋值给call.enqueue的Callback,无论是onResponse还是onFailure都不会被调用。后来在stackoverflow上面发现了文献3,再结合自己的测试,发现根本的原因在于call.enqueue是异步的。当单元测试已经结束时,enqueue的异步处理还没有结束,所以Callback根本没有被调用。那么网络是否执行了呢?通过打开OkhttpClient的log可以看到,MockWebServer的request和response都出现了,说明网络请求已经模拟执行了。产生这个问题跟Robolectric框架的实现有一定的关系,更进一步的具体原因,有兴趣大家可以进一步研究,也许会发现新的思路。
知道是由于异步导致的,那解决的思路就简单了,通过mock手段,将异步执行变成同步执行。那么如何mock呢,我们可以通过retrofit的源码来查看。
通过Retrofit的create方法可以获取service,先来看看create这个方法的实现
public <T> T create(final Class<T> service) {
Utils.validateServiceInterface(service);
if (validateEagerly) {
eagerlyValidateMethods(service);
}
return (T) Proxy.newProxyInstance(service.getClassLoader(), new Class<?>[] { service },
new InvocationHandler() {
private final Platform platform = Platform.get();
@Override public Object invoke(Object proxy, Method method, Object... args)
throws Throwable {
// If the method is a method from Object then defer to normal invocation.
if (method.getDeclaringClass() == Object.class) {
return method.invoke(this, args);
}
if (platform.isDefaultMethod(method)) {
return platform.invokeDefaultMethod(method, service, proxy, args);
}
ServiceMethod serviceMethod = loadServiceMethod(method);
OkHttpCall okHttpCall = new OkHttpCall<>(serviceMethod, args);
return serviceMethod.callAdapter.adapt(okHttpCall);
}
});
} |
从代码可以看出,通过service.getxxx()来获得Call<xxxService>的时候,实际获得的是OkHttpCall。那么call.enqueue实际调用的也是OkHttpCall的enqueue方法,其源码如下:
@Override public void enqueue(final Callback<T> callback) {
if (callback == null) throw new NullPointerException("callback == null");
okhttp3.Call call;
Throwable failure;
synchronized (this) {
if (executed) throw new IllegalStateException("Already executed.");
executed = true;
call = rawCall;
failure = creationFailure;
if (call == null && failure == null) {
try {
call = rawCall = createRawCall();
} catch (Throwable t) {
failure = creationFailure = t;
}
}
}
if (failure != null) {
callback.onFailure(this, failure);
return;
}
if (canceled) {
call.cancel();
}
call.enqueue(new okhttp3.Callback() {
@Override public void onResponse(okhttp3.Call call, okhttp3.Response rawResponse)
throws IOException {
Response<T> response;
try {
response = parseResponse(rawResponse);
} catch (Throwable e) {
callFailure(e);
return;
}
callSuccess(response);
}
@Override public void onFailure(okhttp3.Call call, IOException e) {
try {
callback.onFailure(OkHttpCall.this, e);
} catch (Throwable t) {
t.printStackTrace();
}
}
private void callFailure(Throwable e) {
try {
callback.onFailure(OkHttpCall.this, e);
} catch (Throwable t) {
t.printStackTrace();
}
}
private void callSuccess(Response<T> response) {
try {
callback.onResponse(OkHttpCall.this, response);
} catch (Throwable t) {
t.printStackTrace();
}
}
});
} |
这里通过createRawCall方法来获得真正执行equeue的类,再看看这个方法的实现:
private okhttp3.Call createRawCall() throws IOException {
Request request = serviceMethod.toRequest(args);
okhttp3.Call call = serviceMethod.callFactory.newCall(request);
if (call == null) {
throw new NullPointerException("Call.Factory returned null.");
}
return call;
} |
真正的okhttp3.Call来自于serviceMethod.callFactory.newCall(request),那么serviceMethod.callFactory又是从哪里来的呢。打开ServiceMethod<T>这个类,在构造函数中有如下代码:
this.callFactory = builder.retrofit.callFactory();
说明这个callFactory来自于retrofit.callFactory(),进一步查看Retrofit类的源码:
okhttp3.Call.Factory callFactory = this.callFactory;
if (callFactory == null) {
callFactory = new OkHttpClient();
} |
在通过Retrofit.Builder创建retrofit实例的时候,可以通过下面的方法设置factory实例,如果不设置,默认会创建一个OkHttpClient。
public Builder callFactory(okhttp3.Call.Factory factory) {
this.callFactory = checkNotNull(factory, "factory == null");
return this;
} |
到这里所有的脉络都清楚了,如果创建Retrofit实例时,设置我们自己的callFactory,在该factory中,调用的call.enqueue将根据设置的response直接调用callback中的onResponse或者onFailure方法,从而回避掉异步的问题。具体的实现代码如下:
public class MockFactory extends OkHttpClient {
private MockCall mockCall;
public MockFactory() {
mockCall = new MockCall();
}
public void mockResponse(Response.Builder mockBuilder) {
mockCall.setResponseBuilder(mockBuilder);
}
@Override
public Call newCall(Request request) {
mockCall.setRequest(request);
return mockCall;
}
public class MockCall implements Call {
// Guarded by this.
private boolean executed;
volatile boolean canceled;
/** The application's original request unadulterated by redirects or auth headers. */
Request originalRequest;
Response.Builder mockResponseBuilder;
HttpEngine engine;
protected MockCall() {}
// protected MockCall(Request originalRequest, boolean mockFailure,
// Response.Builder mockResponseBuilder) {
// this.originalRequest = originalRequest;
// this.mockFailure = mockFailure;
// this.mockResponseBuilder = mockResponseBuilder;
// this.mockResponseBuilder.request(originalRequest);
// }
public void setRequest(Request originalRequest) {
this.originalRequest = originalRequest;
}
public void setResponseBuilder(Response.Builder mockResponseBuilder) {
this.mockResponseBuilder = mockResponseBuilder;
}
@Override
public Request request() {
return originalRequest;
}
@Override
public Response execute() throws IOException {
return mockResponseBuilder.request(originalRequest).build();
}
@Override
public void enqueue(Callback responseCallback) {
synchronized (this) {
if (executed) throw new IllegalStateException("Already Executed");
executed = true;
}
int code = mockResponseBuilder.request(originalRequest).build().code();
if (code >= 200 && code < 300) {
try {
if (mockResponseBuilder != null) {
responseCallback.onResponse(this,
mockResponseBuilder.build());
}
} catch (IOException e) {
// Nothing
}
} else {
responseCallback.onFailure(this, new IOException("Mock responseCallback onFailure"));
}
}
@Override
public void cancel() {
canceled = true;
if (engine != null) engine.cancel();
}
@Override
public synchronized boolean isExecuted() {
return executed;
}
@Override
public boolean isCanceled() {
return canceled;
}
}
} |
下面看下单元测试的时候怎么用。
1)通过反射或者mock,修改被测代码中的retrofit实例,调用callFactory来设置上面的MockFactory
2)准备好要返回的response,设置MockFactory的mockResponse,调用被测方法,校验结果
@Test
public void testxxx() throws Exception {
ResponseBody responseBody = ResponseBody.create(MediaType.parse("application/json"),
RestServiceTestHelper.getStringFromFile("xxx.json"));
Response.Builder mockBuilder = new Response.Builder()
.addHeader("Content-Type", "application/json")
.protocol(Protocol.HTTP_1_1)
.code(200)
.body(responseBody);
mMockFactory.mockResponse(mockBuilder);
// call the method to be tested
// verfify if the result is expected
} |
参考文献:
1. robolectric.org
2. https://square.github.io/retrofit/
3. http://stackoverflow.com/questions/37909276/testing-retrofit-2-with-robolectric-callbacks-not-being-called
4. https://riggaroo.co.za/retrofit-2-mocking-http-responses/
----------------------------
原文链接:https://blog.51cto.com/jazka/1880290
程序猿的技术大观园:www.javathinker.net
[这个贴子最后由 flybird 在 2020-03-14 10:10:52 重新编辑]
|
|