android - 如何模拟 Android 仪器测试的共享首选项？

Question

我有一个首选项 util 类，用于在单个位置存储和检索共享首选项中的数据。

Prefutils.java:

public class PrefUtils {
  private static final String PREF_ORGANIZATION = "organization";

  private static SharedPreferences getPrefs(Context context) {
    return PreferenceManager.getDefaultSharedPreferences(context);
  }

  private static SharedPreferences.Editor getEditor(Context context) {
    return getPrefs(context).edit();
  }

  public static void storeOrganization(@NonNull Context context,
      @NonNull Organization organization) {
    String json = new Gson().toJson(organization);
    getEditor(context).putString(PREF_ORGANIZATION, json).apply();
  }

  @Nullable public static Organization getOrganization(@NonNull Context context) {
    String json = getPrefs(context).getString(PREF_ORGANIZATION, null);
    return new Gson().fromJson(json, Organization.class);
  }
}

显示 LoginActivity.java 中 PrefUtils 用法的示例代码:

@Override public void showLoginView() {
    Organization organization = PrefUtils.getOrganization(mActivity);
    mOrganizationNameTextView.setText(organization.getName());
  }

build.gradle 中的 androidTestCompile 依赖项列表:

// Espresso UI Testing dependencies.
  androidTestCompile "com.android.support.test.espresso:espresso-core:$project.ext.espressoVersion"
  androidTestCompile "com.android.support.test.espresso:espresso-contrib:$project.ext.espressoVersion"
  androidTestCompile "com.android.support.test.espresso:espresso-intents:$project.ext.espressoVersion"

  androidTestCompile 'com.google.dexmaker:dexmaker:1.2'
  androidTestCompile 'com.google.dexmaker:dexmaker-mockito:1.2:'

src/androidTest/../LoginScreenTest.java

@RunWith(AndroidJUnit4.class) @LargeTest public class LoginScreenTest {

@Rule public ActivityTestRule<LoginActivity> mActivityTestRule =
      new ActivityTestRule<>(LoginActivity.class);

  @Before public void setUp() throws Exception {
    when(PrefUtils.getOrganization(any()))
          .thenReturn(HelperUtils.getFakeOrganization());
  } 
}

上面返回fakeOrganization的代码不起作用，在登录 Activity 上运行测试会导致mOrganizationNameTextView.setText(organization.getName());定义的行中出现NullPointerException在上面的LoginActivity.java类中。

如何解决上述问题？

Answer 1

方法 1:

使用 Dagger2 将 SharedPreference 公开到应用程序范围，并像在 Activity/fragment 中的 @Inject SharedPreferences mPreferences 一样使用它。

使用上述方法保存(写入)自定义首选项的示例代码:

SharedPreferences.Editor editor = mPreferences.edit();
    editor.putString(PREF_ORGANIZATION, mGson.toJson(organization));
    editor.apply();

要读取自定义首选项:

 String organizationString = mPreferences.getString(PREF_ORGANIZATION, null);
    if (organizationString != null) {
      return mGson.fromJson(organizationString, Organization.class);
    }

如果你像上面那样使用它，就会破坏 DRY 原则，因为代码会在多个地方重复。

<小时/>

方法 2:

此方法基于这样的想法:拥有一个单独的首选项类，例如 StringPreference/BooleanPreference，它提供 SharedPreferences 代码的包装器来保存和检索值。

在继续解决方案之前，请阅读以下帖子以了解详细想法:

1. Persist your data elegantly: U2020 way作者:@tasomaniac
2. Espresso 2.1: ActivityTestRule作者: 千纪
3. Dagger 2 + Espresso 2 + Mockito

代码:

ApplicationModule.java

@Module public class ApplicationModule {
  private final MyApplication mApplication;

  public ApplicationModule(MyApplication application) {
    mApplication = application;
  }

  @Provides @Singleton public Application provideApplication() {
    return mApplication;
  }
}

DataModule.java

@Module(includes = ApplicationModule.class) public class DataModule {

  @Provides @Singleton public SharedPreferences provideSharedPreferences(Application app) {
    return PreferenceManager.getDefaultSharedPreferences(app);
  }
}

GsonModule.java

@Module public class GsonModule {
  @Provides @Singleton public Gson provideGson() {
    GsonBuilder gsonBuilder = new GsonBuilder();
    gsonBuilder.setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES);
    return gsonBuilder.create();
  }
}

ApplicationComponent.java

@Singleton @Component(
    modules = {
        ApplicationModule.class, DataModule.class, GsonModule.class
    }) public interface ApplicationComponent {
  Application getMyApplication();
  SharedPreferences getSharedPreferences();
  Gson getGson();
}

MyApplication.java

public class MyApplication extends Application {
  @Override public void onCreate() {
    initializeInjector();
  }

   protected void initializeInjector() {
    mApplicationComponent = DaggerApplicationComponent.builder()
        .applicationModule(new ApplicationModule(this))
        .build();
  }
}

OrganizationPreference.java

public class OrganizationPreference {

  public static final String PREF_ORGANIZATION = "pref_organization";

  SharedPreferences mPreferences;
  Gson mGson;

  @Inject public OrganizationPreference(SharedPreferences preferences, Gson gson) {
    mPreferences = preferences;
    mGson = gson;
  }

  @Nullable public Organization getOrganization() {
    String organizationString = mPreferences.getString(PREF_ORGANIZATION, null);
    if (organizationString != null) {
      return mGson.fromJson(organizationString, Organization.class);
    }
    return null;
  }

  public void saveOrganization(Organization organization) {
    SharedPreferences.Editor editor = mPreferences.edit();
    editor.putString(PREF_ORGANIZATION, mGson.toJson(organization));
    editor.apply();
  }
}

无论您在哪里需要首选项，只需使用 Dagger @Inject OrganizationPreference mOrganizationPreference; 注入(inject)它即可。

对于androidTest，我用模拟首选项覆盖首选项。以下是我的 android 测试配置:

TestDataModule.java

public class TestDataModule extends DataModule {

  @Override public SharedPreferences provideSharedPreferences(Application app) {
    return Mockito.mock(SharedPreferences.class);
  }
}

MockApplication.java

public class MockApplication extends MyApplication {
  @Override protected void initializeInjector() {
    mApplicationComponent = DaggerTestApplicationComponent.builder()
        .applicationModule(new TestApplicationModule(this))
        .dataModule(new TestDataModule())
        .build();
  }
}

LoginScreenTest.java

@RunWith(AndroidJUnit4.class) public class LoginScreenTest {

@Rule public ActivityTestRule<LoginActivity> mActivityTestRule =
      new ActivityTestRule<>(LoginActivity.class, true, false);

  @Inject SharedPreferences mSharedPreferences;
  @Inject Gson mGson;

 @Before public void setUp() {
    Instrumentation instrumentation = InstrumentationRegistry.getInstrumentation();

    MyApplication app = (MyApplication) instrumentation.getTargetContext().getApplicationContext();
    TestApplicationComponent component = (TestApplicationComponent) app.getAppComponent();
    component.inject(this);
    when(mSharedPreferences.getString(eq(OrganizationPreference.PREF_ORGANIZATION),
        anyString())).thenReturn(mGson.toJson(HelperUtils.getFakeOrganization()));

    mActivityTestRule.launchActivity(new Intent());
  }
}

确保您在 build.gradle 中添加了 dexmaker mockito

androidTestCompile 'com.google.dexmaker:dexmaker:1.2'
androidTestCompile 'com.google.dexmaker:dexmaker-mockito:1.2:'