Code Coverage for Android Testing

Code coverage is a metric that can help you understand how much of your source is tested. Code coverage analysis can only be used for the validation of test cases that are run on the source code and not for the evaluation of the software product.

How is it measured? To calculate the code coverage percentage, simply use the following formula:

Code Coverage Percentage = (Number of lines of code executed by a testing algorithm/Total number of lines of code in a system component) * 100.

JaCoCo Android Studio will invoke or call JaCoCo to do the code coverage reports on your unit tests but you need to perform the following tasks.

Set testCoverageEnabled to true in the build.gradle file Change the Code Coverage Runner to JaCoCo Run Unit Tests / Instrumentation tests with Code Coverage View the Code Coverage To include code coverage in your Android project, set testCoverageEnabled to true in your debug buildTypes in the build.gradle file, see Listing 5, and click on Sync Now after you make the changes.

buildTypes { debug { testCoverageEnabled true } }

buildTypes { debug { testCoverageEnabled true } }

Apply JaCoCo The first thing to do is to create a separate gradle file where we write our configuration. Let’s name it jacoco.gradle and put it on gradle directory

├── app │ └── src ├── gradle │ ├── jacoco.gradle │ └── wrapper

In this file let’s apply the JaCoCo gradle plugin for our modules

// In here we can filter out what modules that we want to cover def coveredProject = subprojects

// configure() method takes a list as an argument and applies the configuration to the projects in this list. configure(coveredProject) { prj ->

// Here we apply jacoco plugin to every project apply plugin: 'jacoco'

// Set Jacoco version jacoco { toolVersion = "0.8.6" }

// Here we create the task to generate Jacoco report task jacocoTestReport(type: JacocoReport) {

// Define what type of report we should generate // If we don't want to process the data further, html should be enough reports { xml.enabled = true html.enabled = true }

// Setup the .class, source, and execution directories final fileFilter = ['/R.class', '/R$.class', '**/BuildConfig.', '/Manifest*.*', 'android//.']

// Include this if you use Kotlin final kotlinTree = fileTree(dir: "${prj.buildDir}/tmp/kotlin-classes/", excludes: fileFilter) final javacTree = fileTree(dir: "${prj.buildDir}/intermediates/javac/", excludes: fileFilter) final mainSrc = "${prj.projectDir}/src/main/java"

sourceDirectories.setFrom files([mainSrc]) classDirectories.setFrom files([kotlinTree, javacTree]) executionData.setFrom fileTree(dir: prj.buildDir, includes: [ 'jacoco/testDebugUnitTest.exec', 'outputs/code-coverage/connected/*coverage.ec' ]) } }

Now we’re ready, to run the unit test and generate the code coverage you can use

$ ./gradlew <module_name>:jacocoTestReport
Aggregate The Coverage Now, to create the aggregated data what you have to do is combine the jacocoReport task Let’s add some more configuration to our jacoco.gradle

apply plugin: 'jacoco'

task jacocoRootReport(type: JacocoReport, group: 'Coverage reports') { def projects = coveredProject

// Here we depend on the jacocoReport task that we created before dependsOn(projects.jacocoTestReport)

final source = files(projects.jacocoTestReport.sourceDirectories)

additionalSourceDirs.setFrom source sourceDirectories.setFrom source

classDirectories.setFrom files(projects.jacocoTestReport.classDirectories) executionData.setFrom files(projects.jacocoTestReport.executionData) reports { xml.enabled = true html.enabled = true html.destination file("${rootProject.rootDir}/jacocoReport") xml.destination file("${rootProject.rootDir}/jacocoReport/report.xml") } doFirst { //noinspection GroovyAssignabilityCheck executionData.setFrom files(executionData.findAll { it.exists() }) } }

apply from: 'gradle/jacoco.gradle' That’s it! To create the aggregated report you can run this in your terminal

$ ./gradlew jacocoRootReport