Run parallel test task using gradle

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.

$rootDir/build.gradle:

subprojects {
    tasks.withType(Test) {
        maxParallelForks = Runtime.runtime.availableProcessors()
    }
}

kotlin gradle dsl

tasks.withType<Test> {
      maxParallelForks = (Runtime.getRuntime().availableProcessors() / 2).coerceAtLeast(1).also {
        println("Setting maxParallelForks to $it")
      }
}

For those of us using Gradle Kotlin DSL in a build.gralde.kts who find themselves here after a google search, I was able to get it to work this way:

tasks.test {
    maxParallelForks = Runtime.getRuntime().availableProcessors()
}

or

tasks.withType<Test> {
        maxParallelForks = (Runtime.getRuntime().availableProcessors() / 2).takeIf { it > 0 } ?: 1
}

as I found here

edit: I ran into some issue as described here. This is (hopefully) my final form:

tasks.withType<Test> {
     systemProperties["junit.jupiter.execution.parallel.enabled"] = true
     systemProperties["junit.jupiter.execution.parallel.mode.default"] = "concurrent" 
     maxParallelForks = (Runtime.getRuntime().availableProcessors() / 2).takeIf { it > 0 } ?: 1
}