Does Gradle run multiple tests in parallel in the same process?

You’ll have to set the forkEvery property to a value greater than zero to start using parallel forks. Each fork is a separate jvm so each will have its own copy of any static variables.

tasks.withType(Test) {
    maxParallelForks = 8
    forkEvery = 10 // each fork will execute a maximum of 10 test classes 
}