ParallelInstancePerTest.kt

import io.kotest.core.config.AbstractProjectConfig
import io.kotest.core.spec.IsolationMode
import io.kotest.core.spec.style.ShouldSpec
import kotlinx.coroutines.delay
import java.time.LocalDateTime
import kotlin.time.ExperimentalTime
import kotlin.time.TimeMark
import kotlin.time.TimeSource

@OptIn(ExperimentalTime::class)
object ProjectConfig : AbstractProjectConfig() {
    override val parallelism = 4
    override val isolationMode = IsolationMode.InstancePerTest

    lateinit var watch: TimeMark

    override fun beforeAll() {
        watch = TimeSource.Monotonic.markNow()
        super.beforeAll()
    }

    override fun afterAll() {
        println("completed tests after ${watch.elapsedNow()}")
        super.afterAll()
    }
}

class ASampleTests : ShouldSpec({
    beforeSpec {
        println("Starting spec at ${LocalDateTime.now()}")
    }

    should("a") {
        delay(5000L)
    }

    should("b") {
        delay(5000L)
    }
})

class BSampleTests : ShouldSpec({
    beforeSpec {
        println("Starting spec at ${LocalDateTime.now()}")
    }

    should("c") {
        delay(5000L)
    }

    should("d") {
        delay(5000L)
    }
})

Starting spec at 2020-10-07T10:23:15.497129
Starting spec at 2020-10-07T10:23:20.672335
Starting spec at 2020-10-07T10:23:15.514699
Starting spec at 2020-10-07T10:23:20.694341
completed tests after 10.3s
completed tests after 10.3s