JaCoCo VS Byte Buddy

I will use here JaCoCo, where also the JaCoCo-Maven-lugin exists for the usage in your Maven builds. This article will show how to configure the code coverage to finally get the results for unit- and integration-tests.

In protection rules, I added build workflow in Require status checks to pass before merging. This is to ensure that before merging code in master branch, build should run successfully. I also added Jacoco Code Coverage to make sure that enough unit tests are available in project and Detekt to make sure that code in project is readable. I added them in build configuration. Even if one of them gives error, build will fail. Whenever, someone push code in pull request, build action will run and check if build is running successfully or not.

Code coverage analysis tools quantify the amount of tested code, serving as a valuable tool to inform on code structure and testing related decisions. We will make use of JaCoCo, JaCoCo produces reports on multiple kinds of code coverage metrics including instructions, line and branch coverage.

One specific example where I regularly use a profile in this way is for configuring code coverage. In all of my Java projects, I use JaCoCo for generating code coverage reports. I use JaCoCo during the Maven test phase. However, while developing I find it useful at times to exclude coverage reporting to reduce the build time. But in my CI/CD workflows in GitHub Actions, I activate the code coverage profile during pull-requests and pushes to the default branch. For pull-requests, my GitHub Actions workflow comments the code coverage on the PR and uploads the coverage report as a workflow artifact, where I can inspect it as necessary. And during a push to the default branch, my workflow updates coverage badges to keep them up to date with the current state of the default branch. I can also activate the code coverage profile locally while developing, such as prior to submitting a pull-request, to ensure that I didn't miss testing something.

In Unit tests, individual software code components are checked if it is working as expected or not. Unit tests isolate a function or module of code and verify its correctness. We can use tools like JaCoCo for Java and Mocha, and Jasmine for NodeJS to generate unit test reports. We can also send these reports to SonarQube which shows us code coverage and the percentage of your code covered by your test cases.

And there is the original jacoco/jacoco: (0.8.7: released this on May 5, 2021), but it's for Java. I'm not sure if we can use it with multiple flavors on Android.

Make sure to also update to Jacoco 0.8.7 to avoid test issues: https://github.com/jacoco/jacoco/releases/tag/v0.8.7

As seen above, the API exposes the user to low-level bytecode manipulation via byte arrays. It would be unwieldy to do it directly. Hence, real-life projects rely on bytecode manipulation libraries. ASM has been the traditional library for this, but it seems that Byte Buddy has superseded it. Note that Byte Buddy uses ASM but provides a higher-level abstraction.

Just a drive-by comment: ByteBuddy is worth a look https://bytebuddy.net/. It is built on top of ASM.

> can you show an example of how you'd parse, say, a .java.in

The canonical way to do such a thing is through the java annotation processing api [1] and using a tool like java poet [2]. Before you did that, you'd probably decide if you wanted to instead use bytecode generation with a library like bytebuddy [3]

But, assuming for some reason, you wanted to torture yourself and actually consume a java.in file and apply a regex, then you'd probably pull out the "maven-replacer-plugin" [4] and configure that for the task at hand. (or use your favorite templating language plugin. There's a million of them).

Though, to be fair, this really isn't something that comes up in regular java programming due to the nature of the ecosystem. Anything you'd want to codegen likely already has a library and anything you didn't would receive (legitimate) push back.

[1] https://www.baeldung.com/java-annotation-processing-builder

[2] https://github.com/square/javapoet

[3] https://bytebuddy.net/

[4] https://github.com/beiliubei/maven-replacer-plugin

Have a look at byte buddy.

If you've ever used libraries like https://github.com/JakeWharton/hugo or https://hibernate.org/ (if you've ever done some backend development) and wondered how do they seem to add some code/logic into your app just by adding some annotation to some method, or if you ever wondered how mocking frameworks like Mockito can change a class behavior for example, then most likely you're interested in a programming technique that allows to modify existing code, usually known as Aspect oriented programming (also known in Java as Bytecode instrumentation) which, even though it might sound intimidating at first, some really cool tools such as Byte Buddy or AspectJ make it quite easy to accomplish.