Test coverage

Once you start writing tests for your Android projects, it is good to know how much of your code base is covered by tests. There are plenty of test coverage tools for Java, but Jacoco is the most popular one. It is also included by default, which makes it easy to get started.

Jacoco

Enabling coverage reports is very easy. You just need to set testCoverageEnabled = true on the build type that you are testing. Enable test coverage for the debug build type like this:

buildTypes {
  debug {
    testCoverageEnabled = true
  }
}

When you enable test coverage, the coverage reports are created when you execute gradlew connectedCheck. The task that creates the report itself is createDebugCoverageReport. Even though it is not documented, and it does not appear in the task list when you run gradlew tasks, it is possible to run it directly. However, because createCoverageReport depends on connectedCheck, you cannot execute them separately. The dependency on connectedCheck also means that you...