[Test apps on Android] Build instrumented unit tests

本文是翻译的Test apps on Android的官方文档 Build instrumented unit tests

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Build instrumented unit tests

构建仪器化的单元测试。

Instrumented unit tests依赖于真实设备或者模拟器运行，它可以利用Android framework API和Supporting API。

Instrumented unit tests 比 local unit test 提供了更高的保真度，但是运行速度比较慢。

因此，建议只在必须针对真实设备行为进行测试的情况下，才使用仪器化测试，AndroidX Test提供了很好的支持。

Set up your testing environment

---

在Android studio project中，必须将instrumented unit tests的类文件放置在module-name /src/androidTest/java/ 中。

AndroidX Test APIs包括，JUnit 4 test runner ( AndroidJUnitRunner) 和API for functional UI tests (Espresso and UI Automator)。

在app/build.gradle中配置依赖库：

	dependencies {
		//AndroidJUnitRunner and JUnit Rules
	    androidTestImplementation 'androidx.test:runner:1.1.0'
	    androidTestImplementation 'androidx.test:rules:1.1.0'
	    // Optional -- Hamcrest library, assert matcher
	    androidTestImplementation 'org.hamcrest:hamcrest-library:1.3'
	    // Optional -- UI testing with Espresso
	    androidTestImplementation 'androidx.test.espresso:espresso-core:3.1.0'
	    // Optional -- UI testing with UI Automator
	    androidTestImplementation 'androidx.test.uiautomator:uiautomator:2.2.0'
	}

在使用Junit 4时，需要明确指定AndroidJUnitRunner为默认的 test instrumentation runner:

	android {
	    defaultConfig {
	        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
	    }
	}

Create an instrumented unit test class

---

instrumented单元测试的类和local单元测试类似，See ➡️。

创建一个基于JUnit 4的instrumented unit test，指定了AndroidJUnit4作为默认的test runner。
因此，不需要在类开头添加 @RunWith(AndroidJUnit4.class)

🌟Note：如果你是基于JUnit 3和Junit 4的混合库，那么需要加上@RunWith(AndroidJUnit4.class)

Sample code snippet：

一个用于验证Parcelable的实现是否正确的测试。

	import android.os.Parcel;
	import android.util.Pair;
	import androidx.test.filters.SmallTest;
	import androidx.test.runner.AndroidJUnit4;
	import com.google.common.truth.Truth.assertThat;
	import java.util.List;
	import org.junit.Before;
	import org.junit.Test;
	import org.junit.runner.RunWith;
	
	// @RunWith is required only if you use a mix of JUnit3 and JUnit4.
	@RunWith(AndroidJUnit4.class)
	@SmallTest
	public class LogHistoryAndroidUnitTest {
	
	    public static final String TEST_STRING = "This is a string";
	    public static final long TEST_LONG = 12345678L;
	    private LogHistory mLogHistory;
	
	    @Before
	    public void createLogHistory() {
	        mLogHistory = new LogHistory();
	    }
	
	    @Test
	    public void logHistory_ParcelableWriteRead() {
	        // Set up the Parcelable object to send and receive.
	        mLogHistory.addEntry(TEST_STRING, TEST_LONG);
	
	        // Write the data.
	        Parcel parcel = Parcel.obtain();
	        mLogHistory.writeToParcel(parcel, mLogHistory.describeContents());
	
	        // After you're done with writing, you need to reset the parcel for reading.
	        parcel.setDataPosition(0);
	
	        // Read the data.
	        LogHistory createdFromParcel = LogHistory.CREATOR.createFromParcel(parcel);
	        List<Pair<String, Long>> createdFromParcelData
	                = createdFromParcel.getData();
	
	        // Verify that the received data is correct.
	        assertThat(createdFromParcelData.size()).isEqualTo(1);
	        assertThat(createdFromParcelData.get(0).first).isEqualTo(TEST_STRING);
	        assertThat(createdFromParcelData.get(0).second).isEqaulTo(TEST_LONG);
	    }
	}

Create a test suite

可以将一组测试类归为一个测试套件，然后一起运行这些测试。

一个测试套件类也位于测试包中，其包名通常以 .suite 结尾，例如：com.example.android.testing.mysample.suite

Sample code snippet：

	import com.example.android.testing.mysample.CalculatorAddParameterizedTest;
	import com.example.android.testing.mysample.CalculatorInstrumentationTest;
	import org.junit.runner.RunWith;
	import org.junit.runners.Suite;
	
	// Runs all unit tests.
	@RunWith(Suite.class)
	@Suite.SuiteClasses({CalculatorInstrumentationTest.class,
	        CalculatorAddParameterizedTest.class})
	public class UnitTestSuite {}

Run instrumented unit tests

---

To run your instrumented unit tests, follow these steps:

• Be sure your project is synchronized with Gradle by clicking Sync Project in the toolbar.

• Run your test in one of the following ways:

  • To run a single test, open the Project window, and then right-click a test and click Run
  • To test all methods in a class, right-click a class or method in the test file and click Run
  • To run all tests in a directory, right-click on the directory and select Run tests

Android Gradle插件会编译默认目录（src/androidTest/java/）中的仪器化单元测试代码，生成一个测试APK和生产APK，并安装在所连接的设备或者模拟器上，然后运行测试。最后，Android Studio在“ Run” 窗口中显示结果。

Firebase Test Lab

emmm，we don’t f**k need it😓！

Sample

• Instrumented Unit Tests Code Samples