目前的Android單元測(cè)試，很多都基于Roboletric框架，回避了Instrumentation test必須啟動(dòng)虛擬機(jī)或者真機(jī)的麻煩，執(zhí)行效率大大提高。這里不討論測(cè)試框架的選擇問題，網(wǎng)絡(luò)上有很多關(guān)于此類的資料。同時(shí)，現(xiàn)在幾乎所有的App都會(huì)進(jìn)行網(wǎng)絡(luò)數(shù)據(jù)通信，Retrofit2就是其中非常方便的一個(gè)網(wǎng)絡(luò)框架，遵循Restful接口設(shè)計(jì)。如此，再進(jìn)行Android單元測(cè)試時(shí)，就必然需要繞過Retrofit的真實(shí)網(wǎng)絡(luò)請(qǐng)求，mock出不同的response來進(jìn)行本地邏輯測(cè)試。
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retrofit官方出過單元測(cè)試的方法和介紹，詳見參考文獻(xiàn)4，介紹的非常細(xì)致。但是該方法是基于Instrumentation的，如果基于Robolectric框架，對(duì)于異步的請(qǐng)求就會(huì)出現(xiàn)問題，在stackoverflow上面有關(guān)于異步問題的描述，也給出了一個(gè)解決方法，但是需要對(duì)源碼進(jìn)行改動(dòng)，所以不完美。本文將針對(duì)Robolectric+Retrofit2的單元測(cè)試過程中異步問題如何解決，提出一種更完美的解決方法。有理解不當(dāng)?shù)?，后者更好的方案，歡迎大家提出指正。
一般使用retrofit2的時(shí)候，會(huì)出現(xiàn)一下代碼片段
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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 call = service.getxxx();
call.enqueue(new Callback() {
@Override
public void onResponse(Call call, Response response) {
// Deal with the successful case
}
@Override
public void onFailure(Call call, Throwable t) {
// Deal with the failure case
}
});
} 單元測(cè)試會(huì)測(cè)試testMethod方法，觸發(fā)后根據(jù)不同的response，校驗(yàn)對(duì)應(yīng)的邏輯處理，如上面的“// Deal with the successful case” 和 “// Deal with the failure case”。為了達(dá)到這個(gè)目的，需要實(shí)現(xiàn)一下兩點(diǎn)：1）當(dāng)觸發(fā)該方法時(shí)，不會(huì)走真實(shí)的網(wǎng)絡(luò)；2）可以mock不同的response進(jìn)行測(cè)試
第一點(diǎn)可以借助MockWebServer來實(shí)現(xiàn)，具體的實(shí)現(xiàn)方法可以參考文獻(xiàn)4，這里不展開了，重點(diǎn)看下第二點(diǎn)。在文獻(xiàn)4中的sample#1，通過一個(gè)json文件，清晰簡(jiǎn)單的表明了測(cè)試的目的，所以我們也希望用這種方式。但是當(dāng)實(shí)現(xiàn)后測(cè)試卻發(fā)現(xiàn)，上面賦值給call.enqueue的Callback，無論是onResponse還是onFailure都不會(huì)被調(diào)用。后來在stackoverflow上面發(fā)現(xiàn)了文獻(xiàn)3，再結(jié)合自己的測(cè)試，發(fā)現(xiàn)根本的原因在于call.enqueue是異步的。當(dāng)單元測(cè)試已經(jīng)結(jié)束時(shí)，enqueue的異步處理還沒有結(jié)束，所以Callback根本沒有被調(diào)用。那么網(wǎng)絡(luò)是否執(zhí)行了呢？通過打開OkhttpClient的log可以看到，MockWebServer的request和response都出現(xiàn)了，說明網(wǎng)絡(luò)請(qǐng)求已經(jīng)模擬執(zhí)行了。產(chǎn)生這個(gè)問題跟Robolectric框架的實(shí)現(xiàn)有一定的關(guān)系，更進(jìn)一步的具體原因，有興趣大家可以進(jìn)一步研究，也許會(huì)發(fā)現(xiàn)新的思路。
知道是由于異步導(dǎo)致的，那解決的思路就簡(jiǎn)單了，通過mock手段，將異步執(zhí)行變成同步執(zhí)行。那么如何mock呢，我們可以通過retrofit的源碼來查看。
通過Retrofit的create方法可以獲取service，先來看看create這個(gè)方法的實(shí)現(xiàn)
publicT create(final Class 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); } }); }
從代碼可以看出，通過service.getxxx()來獲得Call
@Override public void enqueue(final Callbackcallback) { 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 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 response) { try { callback.onResponse(OkHttpCall.this, response); } catch (Throwable t) { t.printStackTrace(); } } }); }
這里通過createRawCall方法來獲得真正執(zhí)行equeue的類，再看看這個(gè)方法的實(shí)現(xiàn)：
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來自于serviceMethod.callFactory.newCall(request)，那么serviceMethod.callFactory又是從哪里來的呢。打開ServiceMethod
this.callFactory = builder.retrofit.callFactory();
說明這個(gè)callFactory來自于retrofit.callFactory()，進(jìn)一步查看Retrofit類的源碼：
okhttp3.Call.Factory callFactory = this.callFactory;
if (callFactory == null) {
callFactory = new OkHttpClient();
}在通過Retrofit.Builder創(chuàng)建retrofit實(shí)例的時(shí)候，可以通過下面的方法設(shè)置factory實(shí)例，如果不設(shè)置，默認(rèn)會(huì)創(chuàng)建一個(gè)OkHttpClient。
public Builder callFactory(okhttp3.Call.Factory factory) {
this.callFactory = checkNotNull(factory, "factory == null");
return this;
}到這里所有的脈絡(luò)都清楚了，如果創(chuàng)建Retrofit實(shí)例時(shí)，設(shè)置我們自己的callFactory，在該factory中，調(diào)用的call.enqueue將根據(jù)設(shè)置的response直接調(diào)用callback中的onResponse或者onFailure方法，從而回避掉異步的問題。具體的實(shí)現(xiàn)代碼如下：
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;
}
}
}下面看下單元測(cè)試的時(shí)候怎么用。
1）通過反射或者mock，修改被測(cè)代碼中的retrofit實(shí)例，調(diào)用callFactory來設(shè)置上面的MockFactory
2）準(zhǔn)備好要返回的response，設(shè)置MockFactory的mockResponse，調(diào)用被測(cè)方法，校驗(yàn)結(jié)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
}參考文獻(xiàn)：
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/
