Run tests concurrently

build.sbt

@@ -34,6 +34,9 @@ val organizeImportsVersion     = "0.6.0"
 // See https://github.com/akka/akka-http/pull/3995 and https://github.com/akka/akka-http/pull/3995#issuecomment-1026978593
 ThisBuild / libraryDependencySchemes += "org.scala-lang.modules" %% "scala-xml" % "always"
 
+concurrentRestrictions in Global += Tags.limit(Tags.ForkedTestGroup, EvaluateTask.SystemProcessors)
+ThisBuild / Test / testForkedParallel := true
+
 val flagsFor12 = Seq(
   "-Xlint:_",
   "-Ywarn-infer-any",

core/src/test/scala/io/aiven/guardian/kafka/KafkaClusterTest.scala

@@ -5,7 +5,6 @@ import akka.kafka.ConsumerSettings
 import akka.kafka.ProducerSettings
 import akka.kafka.scaladsl.Producer
 import akka.stream.scaladsl.Source
-import com.dimafeng.testcontainers.ForAllTestContainer
 import com.dimafeng.testcontainers.KafkaContainer
 import io.aiven.guardian.akka.AkkaStreamTestKit
 import io.aiven.guardian.kafka.TestUtils.KafkaFutureToCompletableFuture
@@ -25,13 +24,13 @@ import scala.jdk.CollectionConverters._
 import scala.jdk.FutureConverters._
 import scala.language.postfixOps
 
-trait KafkaClusterTest extends ForAllTestContainer with AkkaStreamTestKit { this: Suite =>
+trait KafkaClusterTest extends AkkaStreamTestKit { this: Suite =>
 
   /** Timeout constant to wait for both Akka Streams plus initialization of consumer/kafka cluster
     */
   val KafkaInitializationTimeoutConstant: FiniteDuration = AkkaStreamInitializationConstant + (2.5 seconds)
 
-  override lazy val container: KafkaContainer = new KafkaContainer()
+  lazy val container: KafkaContainer = KafkaClusterTest.container
 
   def baseKafkaConfig: Some[ConsumerSettings[Array[Byte], Array[Byte]] => ConsumerSettings[Array[Byte], Array[Byte]]] =
     Some(
@@ -80,22 +79,7 @@ trait KafkaClusterTest extends ForAllTestContainer with AkkaStreamTestKit { this
     ).runWith(Producer.plainSink(producerSettings))
   }
 
-  protected var adminClient: AdminClient = _
-
-  override def afterStart(): Unit = {
-    super.afterStart()
-    adminClient = AdminClient.create(
-      Map[String, AnyRef](
-        CommonClientConfigs.BOOTSTRAP_SERVERS_CONFIG -> container.bootstrapServers
-      ).asJava
-    )
-  }
-
-  override def beforeStop(): Unit = {
-    adminClient.close()
-    super.beforeStop()
-  }
-
+  import KafkaClusterTest.adminClient
   def createTopics(topics: Set[String])(implicit executionContext: ExecutionContext): Future[Unit] =
     for {
       currentTopics <- adminClient.listTopics().names().toCompletableFuture.asScala
@@ -118,3 +102,18 @@ trait KafkaClusterTest extends ForAllTestContainer with AkkaStreamTestKit { this
 
   case object TerminationException extends Exception("termination-exception")
 }
+
+object KafkaClusterTest {
+  protected var adminClient: AdminClient = _
+
+  protected lazy val container: KafkaContainer = {
+    val con = new KafkaContainer()
+    con.start()
+    adminClient = AdminClient.create(
+      Map[String, AnyRef](
+        CommonClientConfigs.BOOTSTRAP_SERVERS_CONFIG -> con.bootstrapServers
+      ).asJava
+    )
+    con
+  }
+}