junit - Run parallel test task using gradle

Question

We use JUnit as a test framework. We have many projects. We use gradle (version 1.12) as a build tool. To run the unit tests in parallel using gradle we use the below script in every project under test task.

maxParallelForks = Runtime.runtime.availableProcessors()

Ex:

test {    
  maxParallelForks = Runtime.runtime.availableProcessors()       
}

We also maintain the single gradle.properties file.

Is it possible to define test.maxParallelForks = Runtime.runtime.availableProcessors() in gradle.properties file rather than defining it in each build.gradle file under test task?

Answer 1

The accepted answer above works but the Gradle documentation here suggests you use

maxParallelForks = Runtime.runtime.availableProcessors().intdiv(2) ?: 1

I tried both and after testing both on a 2.3 GHz Intel Core i7 Mac Book Pro with 16GB RAM (4 cores with hyperthreading)

test {
    maxParallelForks = Runtime.runtime.availableProcessors()
}

and

test {    
    maxParallelForks = Runtime.runtime.availableProcessors().intdiv(2) ?: 1      
}

The approach suggested by Gradle documentation produced faster response times for our unit test suite: 7 minutes vs. 8 minutes (compared to the original 13 minutes). In addition my Mac CPU didn't get pegged and the fan didn't kick off.

I assume there is either contention on a shared resource - even if it is only the machine one which we are running the unit tests.