Getting Jacoco to work with Dagger
January 16, 2015Writing tests for your code provides you with a number of development benefits, from proving that your code meets set requirements to ensuring that future code changes don’t introduce bugs or break existing functionality. It’s also important to know how much of your code is covered by your tests and what areas in your code aren’t yet covered.
Jacoco is a framework that creates code coverage reports that show you how much of your code has or has not been touched in your tests. This post is an excellent guide to setting up your Android Gradle project to use Jacoco.
To generate the Jacoco test coverage report, execute the following in the commandline:
./gradlew cleanTest test jacocoTestReport
If you’re using Dagger in your Android Gradle project, you might encounter the following error:
FAILURE: Build failed with an exception. * What went wrong: Execution failed for task ':app:jacocoTestReport'. > Error while creating report
To dig deeper into this error, execute the same command with the stacktrace option:
./gradlew cleanTest test jacocoTestReport --stacktrace
In the stack trace, you’ll see an entry similar to this:
Caused by: java.io.FileNotFoundException: /app/build/intermediates/classes/debug/com/yourproject/AndroidModule$ModuleAdapter$ProvideAccountManagerProvidesAdapter.class (No such file or directory) at org.apache.tools.ant.types.resources.FileResource.getInputStream(FileResource.java:217) at org.jacoco.ant.ReportTask.createBundle(ReportTask.java:568) at org.jacoco.ant.ReportTask.createReport(ReportTask.java:547) at org.jacoco.ant.ReportTask.execute(ReportTask.java:494) ... 67 more
Jacoco is expecting to find generated files with a single “$” in their name, but Dagger generates files with “$$” in their name. However, we don’t need to check test coverage in these generated classes, so we can tell Jacoco to ignore these files by adding the following to the “excludes” array (in addition to any existing entries) in the fileTree passed to “classDirectories”, like so:
classDirectories = fileTree( dir: '../app/build/intermediates/classes/debug', excludes: [ '**/*InjectAdapter*.*', '**/*StaticInjection*.*', '**/*ModuleAdapter*.*' ] )
Stay in the loop with our latest content!
Select the topics you’re interested to receive our new relevant content in your inbox. Don’t worry, we won’t spam you.

Download a collection of 3 key articles on the state of digital today
April 14, 2020As presented by Forbes. Download the top-3 most popular articles published by Michigan Software Labs.
Read more
Time Check
June 6, 2019Read Karl's blog post about an interesting development challenge related to time.
Read more
Development Practice Lead, Josh Friend on What's Possible in Technology
December 12, 2019As the Development Practice Lead at Michigan Software Labs, I’ve had the unique opportunity to have a small role in most of the digital products that we develop for our clients. This has given me the perspective that nearly anything is possible when it comes to what a client wants to develop - technology is rarely the barrier stopping progress.
Read more