Jacoco在Android系统应用测试中覆盖率一直为0的解决方案

问题

普通应用Gradle配置Jacoco，运行createDebugAndroidTestCoverageReport,能够正常输出覆盖率报告,报告路径为：
build/reports/coverage/debug/index.html。查看build/outputs/code-coverage/connected/*-coverage.ec，存在运行覆盖数据。

android {
    compileSdkVersion 27
    defaultConfig {
        applicationId "example.api.com.myapplication2"
        minSdkVersion 24
        targetSdkVersion 27
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        debug{
            testCoverageEnabled true
        }
    }
 }

在AndroidManifest中增加android:sharedUserId=”android.uid.system”,输出报告覆盖率一直为0。查看build/outputs/code-coverage/connected/*-coverage.ec 一直为空。

Jacoco原理

参考：https://blog.csdn.net/allan_shore_ma/article/details/80053340
简单来说：
debug模式下增加testCoverageEnabled true 后Gradle自动利用 jacoco插件在生成最终的目标文件之前，对源app Class文件进行插桩，生成最终的目标文件，执行目标文件以后得到覆盖执行数据。通过执行createDebugAndroidTestCoverageReport，在测试程序结束后会通过反射调用org.jacoco.agent.rt.RT.getAgent().getExecutionData(false) 获取到二进制数据并将此文件数据同步到uild/outputs/code-coverage/connected/${deviceName}-coverage.ec中。然后Gralde将此文件与build/intermediates/classes文件进行比较标记出类和行号，同时与src对比，输出报告到build/reports/coverage/debug/index.html

解决办法

因为代码插桩原理都是一样的，运行后也会有jacoco的覆盖数据信息。但实际系统应用获取到的coverage.ec为空，可以猜测以为权限问题，此数据无法直接导入到build/outputs/code-coverage/connected/*-coverage.ec。系统应用以及它的测试应用已经有写sd卡权限，可以通过sd卡作为中转。在测试用例执行完成的恰当时机，刷新sd卡的coverage.ec。测试结束后导出数据到build/outputs/code-coverage/connected/coverage.ec。最后执行jacoco的生成报告任务。
在测试用例执行完的恰当时机刷新coverage.ec，主要代码：

public class PushTestReport {

    public static String getSDPath(){
        File sdDir = null;
        boolean sdCardExist = Environment.getExternalStorageState()
                .equals(android.os.Environment.MEDIA_MOUNTED);
        if(sdCardExist)
        {
            sdDir = Environment.getExternalStorageDirectory();
        }
        return sdDir.toString();
    }


    public static void createReport() {

        String dir = getSDPath();
        String path = dir + "/coverage.ec";
        Log.d("jacoco","createReport:"+path);
        File file = new File(path);
        if (!file.exists()) {
            try {
                file.createNewFile();
            } catch (IOException e) {
                e.printStackTrace();
                Log.e("jacoco","pushReport,error:"+e.getMessage());
            }
        }

        OutputStream out = null;
        try {
            out = new FileOutputStream(path, false);
            Object agent = Class.forName("org.jacoco.agent.rt.RT")
                    .getMethod("getAgent")
                    .invoke(null);
            byte[] bytes = (byte[])agent.getClass().getMethod("getExecutionData", boolean.class)
                    .invoke(agent, false);

            Log.d("jacoco","pushReport,bytes:"+bytes.length);
            out.write(bytes);
        } catch (Exception e) {
            e.printStackTrace();
            Log.e("jacoco","pushReport,error:"+e.getMessage());
        } finally {
            if (out != null) {
                try {
                    out.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

调用时机tearDown()：

 @After
    public void tearDown() throws Exception {
        PushTestReport.createReport();
    }

以及TestRule运行完用例处：

@Override
    public Statement apply(final Statement base, final Description description) {
        return new Statement() {
            @Override
            public void evaluate() throws Throwable {
                base.evaluate();
                PushTestReport.createReport();

            }
        };
    }

build.gradle如下：

task preJacocoTestReport(type: Exec) {
    executable 'sh'
    args "pre-jacoco-report.sh"
}


task jacocoTestReport(type: JacocoReport,dependsOn: preJacocoTestReport) {

    group = "Reporting"
    description = "Generate Jacoco coverage reports after running tests."
    reports {
        xml.enabled = true
        html.enabled = true
    }


    def coverageSourceDirs = [
            '../app/src/main/java'
    ]

    def excludeClasses = ['**/R*.class',
                          '**/*$InjectAdapter.class',
                          '**/*$ModuleAdapter.class',
                          '**/*$ViewInjector*.class',
                          '**/BuildConfig.class'
    ]

    classDirectories = fileTree(dir: '../app/build/intermediates/classes/debug',excludes: excludeClasses)
    
    sourceDirectories = files(coverageSourceDirs)
    executionData = files("$buildDir/outputs/code-coverage/connected/coverage.ec")

    doFirst {
        new File("$buildDir/intermediates/classes/").eachFileRecurse { file ->
            if (file.name.contains('$$')) {
                file.renameTo(file.path.replace('$$', '$'))
            }
        }
    }
}

pre-jacoco-report.sh脚本：

#!/usr/bin/env bash
#当前在环境为Project/app目录
rm -f build/outputs/code-coverage/connected/coverage.ec
adb pull /storage/emulated/0/coverage.ec build/outputs/code-coverage/connected/

运行以下任务输出报告：build/reports/jacoco/jacocoTestReport/html/index.html

gradle createDebugCoverageReport -p Project/app
gradle jacocoTestReport -p Project/app

子模块覆盖率统计注意

如果想要子模块的覆盖率也统计进去

1. 子模块的build.gradle中也增加testCoverageEnabled true

2. src也要包含子模块的src，例如：

   def coverageSourceDirs = [
   ‘…/**/src/main/java’
   ]

3. class也要包含子模块的class:

   classDirectories += fileTree(dir: ‘…/subMoudle1/build/intermediates/classes/debug’,excludes: excludeClasses)
   classDirectories += fileTree(dir: ‘…/subMoudle2/build/intermediates/classes/debug’,excludes: excludeClasses)

插曲

Jacoco一直报错：

08-20 13:47:35.971 25869-25869/com.gs.service W/System.err: java.io.FileNotFoundException: /jacoco.exec (Read-only file system)
        at java.io.FileOutputStream.open(Native Method)
        at java.io.FileOutputStream.(FileOutputStream.java:221)
        at org.jacoco.agent.rt.internal_8ff85ea.output.FileOutput.openFile(FileOutput.java:67)
        at org.jacoco.agent.rt.internal_8ff85ea.output.FileOutput.startup(FileOutput.java:49)
08-20 13:47:35.972 25869-25869/com.gs.service W/System.err:     at org.jacoco.agent.rt.internal_8ff85ea.Agent.startup(Agent.java:122)
        at org.jacoco.agent.rt.internal_8ff85ea.Agent.getInstance(Agent.java:50)
        at org.jacoco.agent.rt.internal_8ff85ea.Offline.(Offline.java:31)
        at org.jacoco.agent.rt.internal_8ff85ea.Offline.getProbes(Offline.java:51)

修改文件权限或者增加/jacoco-agent.properties 里面destfile=/mnt/sdcard/jacoco.exec并不能解决问题。然而此异常也并不影响覆盖率的统计。后续仍可深究。