背景

手工测试过程中有个测试场景需要删除测试设备上某个 Android feature，往上搜索了一圈没找到有效的操作方法。获取 Android 设备所有的 feature 可以通过 adb 命令 pm list features 或者 Android 代码 Context.getPackageManager().getSystemAvailableFeatures()，但都没有对应的修改方法。

既然 feature 是从 Context 获取的，那能不能构造一个只包含我想要的 feature 的 Context 呢。顺着这个思路，有了下面的方案。

方案设计

单元测试常用的 Mock 技术，就是来构造假/模拟对象的。但如果完全构造，又担心和真实环境差别较大，测试结果不可靠。能不能从真实 Android 设备中获取真实的 Context，把不想要的 feature 去除，再给到被测试方法中呢？

答案是肯定的，通过选用流行的 Mock 组件Mockito ，官网上给出了下面 2 种 Mock Java 对象的方式：

mock()/@Mock: create mock
spy()/@Spy: partial mocking, real methods are invoked but still can be verified and stubbed

可以看到 Spy 这种 Mock 方式可完美地解决我的需求。

实现（简化版需求）

业务需求说明

获取所有 Android Features 并把 feature name 打印在日志中，使用 adb 命令的效果如下：

➜  study git:(master) ✗ adb shell pm list features                                    
feature:reqGlEsVersion=0x30002
feature:android.hardware.audio.output
feature:android.hardware.bluetooth
feature:android.hardware.bluetooth_le
feature:android.hardware.camera
feature:android.hardware.camera.any
feature:android.hardware.camera.autofocus
feature:android.hardware.camera.capability.manual_post_processing
feature:android.hardware.camera.capability.manual_sensor
feature:android.hardware.camera.capability.raw
feature:android.hardware.camera.flash
feature:android.hardware.camera.front
feature:android.hardware.camera.level.full
feature:android.hardware.faketouch
feature:android.hardware.location
feature:android.hardware.location.gps
feature:android.hardware.location.network
feature:android.hardware.microphone
feature:android.hardware.nfc.any
feature:android.hardware.opengles.aep
feature:android.hardware.ram.normal
feature:android.hardware.screen.landscape
feature:android.hardware.screen.portrait
feature:android.hardware.sensor.accelerometer
feature:android.hardware.sensor.compass
feature:android.hardware.sensor.light
feature:android.hardware.sensor.proximity
feature:android.hardware.sensor.stepcounter
feature:android.hardware.telephony
feature:android.hardware.telephony.cdma
feature:android.hardware.telephony.gsm
feature:android.hardware.touchscreen
feature:android.hardware.touchscreen.multitouch
feature:android.hardware.touchscreen.multitouch.distinct
feature:android.hardware.touchscreen.multitouch.jazzhand
feature:android.hardware.usb.accessory
feature:android.hardware.usb.host
feature:android.hardware.vulkan.compute
feature:android.hardware.vulkan.level
feature:android.hardware.vulkan.version=4194307
feature:android.hardware.wifi
feature:android.hardware.wifi.direct
feature:android.software.activities_on_secondary_displays
feature:android.software.app_widgets
feature:android.software.autofill
feature:android.software.backup
feature:android.software.companion_device_setup
feature:android.software.connectionservice
feature:android.software.cts
feature:android.software.device_admin
feature:android.software.file_based_encryption
feature:android.software.input_methods
feature:android.software.live_wallpaper
feature:android.software.managed_users
feature:android.software.midi
feature:android.software.picture_in_picture
feature:android.software.print
feature:android.software.securely_removes_users
feature:android.software.sip
feature:android.software.sip.voip
feature:android.software.verified_boot
feature:android.software.voice_recognizers
feature:android.software.webview

业务需求代码实现

public class FeaturesUtil {
    private static final String TAG = "FeaturesUtil";

    public static void getFeatures(Context context) {
        PackageManager packageManager = context.getPackageManager();
        FeatureInfo[] featureInfos = packageManager.getSystemAvailableFeatures();

        for (FeatureInfo featureInfo : featureInfos) {
            Log.i(TAG, "feature: " + featureInfo.name);
        }
    }
}

测试代码实现 (去除 bluetooth feature)

@Spy
Context context = InstrumentationRegistry.getInstrumentation().getTargetContext();;

@Spy
PackageManager packageManager = context.getPackageManager();

    @Test
public void getFeatures() {
    // 去除bluetooth feature
    FeatureInfo[] mockedFeatureInfos = removeFeature(packageManager.getSystemAvailableFeatures(),
            Arrays.asList("android.hardware.bluetooth", "android.hardware.bluetooth_le"));

    when(packageManager.getSystemAvailableFeatures()).thenReturn(mockedFeatureInfos);
    when(context.getPackageManager()).thenReturn(packageManager);

    FeaturesUtil.getFeatures(context);
}

/**
 * 根据feature name删除一个或多个feature
 *
 * @param featureInfos FeatureInfo数组
 * @param featureNames 字符串列表，每个元素是要删除的FeatureInfo的name
 * @return 删除之后的FeatureInfo数组
 */
private FeatureInfo[] removeFeature(FeatureInfo[] featureInfos, List<String> featureNames) {
    List<FeatureInfo> featureInfoList = new ArrayList();

    for (FeatureInfo featureInfo :
         featureInfos) {
        if (featureInfo.name != null && !(featureNames.contains(featureInfo.name))) {
            featureInfoList.add(featureInfo);
        }
    }

    return featureInfoList.toArray(new FeatureInfo[featureInfoList.size()]);
}

运行测试代码后 Logcat 输出

可以看到 bluetooth 相关的 feature 已经没有了

2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.hardware.sensor.proximity
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.hardware.sensor.accelerometer
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.hardware.faketouch
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.hardware.usb.accessory
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.hardware.telephony.cdma
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.software.backup
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.hardware.touchscreen
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.hardware.touchscreen.multitouch
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.software.print
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.software.activities_on_secondary_displays
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.software.voice_recognizers
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.software.picture_in_picture
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.hardware.opengles.aep
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.hardware.camera.autofocus
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.hardware.telephony.gsm
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.software.sip.voip
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.hardware.usb.host
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.hardware.audio.output
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.software.verified_boot
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.hardware.camera.flash
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.hardware.camera.front
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.hardware.screen.portrait
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.hardware.microphone
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.software.autofill
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.software.securely_removes_users
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.hardware.sensor.compass
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.hardware.touchscreen.multitouch.jazzhand
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.software.app_widgets
2021-04-07 13:23:39.266 16238-16268/? I/FeaturesUtil: feature: android.software.input_methods
2021-04-07 13:23:39.267 16238-16268/? I/FeaturesUtil: feature: android.hardware.sensor.light
2021-04-07 13:23:39.267 16238-16268/? I/FeaturesUtil: feature: android.hardware.vulkan.version
2021-04-07 13:23:39.267 16238-16268/? I/FeaturesUtil: feature: android.software.companion_device_setup
2021-04-07 13:23:39.267 16238-16268/? I/FeaturesUtil: feature: android.software.device_admin
2021-04-07 13:23:39.267 16238-16268/? I/FeaturesUtil: feature: android.hardware.camera
2021-04-07 13:23:39.267 16238-16268/? I/FeaturesUtil: feature: android.hardware.screen.landscape
2021-04-07 13:23:39.267 16238-16268/? I/FeaturesUtil: feature: android.hardware.ram.normal
2021-04-07 13:23:39.267 16238-16268/? I/FeaturesUtil: feature: android.software.managed_users
2021-04-07 13:23:39.267 16238-16268/? I/FeaturesUtil: feature: android.software.webview
2021-04-07 13:23:39.267 16238-16268/? I/FeaturesUtil: feature: android.hardware.sensor.stepcounter
2021-04-07 13:23:39.267 16238-16268/? I/FeaturesUtil: feature: android.hardware.camera.capability.manual_post_processing
2021-04-07 13:23:39.267 16238-16268/? I/FeaturesUtil: feature: android.hardware.camera.any
2021-04-07 13:23:39.267 16238-16268/? I/FeaturesUtil: feature: android.hardware.camera.capability.raw
2021-04-07 13:23:39.267 16238-16268/? I/FeaturesUtil: feature: android.hardware.vulkan.compute
2021-04-07 13:23:39.267 16238-16268/? I/FeaturesUtil: feature: android.software.connectionservice
2021-04-07 13:23:39.267 16238-16268/? I/FeaturesUtil: feature: android.hardware.touchscreen.multitouch.distinct
2021-04-07 13:23:39.267 16238-16268/? I/FeaturesUtil: feature: android.hardware.location.network
2021-04-07 13:23:39.267 16238-16268/? I/FeaturesUtil: feature: android.software.cts
2021-04-07 13:23:39.267 16238-16268/? I/FeaturesUtil: feature: android.software.sip
2021-04-07 13:23:39.267 16238-16268/? I/FeaturesUtil: feature: android.hardware.camera.capability.manual_sensor
2021-04-07 13:23:39.267 16238-16268/? I/FeaturesUtil: feature: android.hardware.camera.level.full
2021-04-07 13:23:39.267 16238-16268/? I/FeaturesUtil: feature: android.hardware.wifi.direct
2021-04-07 13:23:39.267 16238-16268/? I/FeaturesUtil: feature: android.software.live_wallpaper
2021-04-07 13:23:39.267 16238-16268/? I/FeaturesUtil: feature: android.hardware.location.gps
2021-04-07 13:23:39.267 16238-16268/? I/FeaturesUtil: feature: android.software.midi
2021-04-07 13:23:39.267 16238-16268/? I/FeaturesUtil: feature: android.hardware.nfc.any
2021-04-07 13:23:39.268 16238-16268/? I/FeaturesUtil: feature: android.hardware.wifi
2021-04-07 13:23:39.268 16238-16268/? I/FeaturesUtil: feature: android.hardware.location
2021-04-07 13:23:39.268 16238-16268/? I/FeaturesUtil: feature: android.hardware.vulkan.level
2021-04-07 13:23:39.268 16238-16268/? I/FeaturesUtil: feature: android.hardware.telephony
2021-04-07 13:23:39.268 16238-16268/? I/FeaturesUtil: feature: android.software.file_based_encryption
2021-04-07 13:23:39.269 16238-16268/? I/TestRunner: finished: getFeatures(com.aniu.featuresmock.FeaturesUtilTest)

总结

不直接使用 Mock，而是使用 Spy，最大限度保持测试环境真实可靠，从而保证测试效果
测试代码不要放在 test 目录，要放在 androidTest 目录，保证在真实设备上跑（不然代码也会报错）。目录结构如下：

↙↙↙阅读原文可查看相关链接，并与作者交流