'Unable to load a Suite class' while running ScalaTest in IntelliJ

Question

I'm having some issues today with running a simple TestKit test in Intellij. The tests are for Scala code (I have the Scala plug-in for Intellij) and are based on Ray Roestenburg's example.

The Intellij project was created using a "Maven Module" which I then added all the dependencies to and created my project. The tests are located in the following place:

ActorBlast/src/test/scala/basicTest.scala

I'm basically "right-clicking" on the test and selecting "Run". What I get is the following error:

"C:\Program Files\Java\jdk1.7.0_25\bin\java" -Didea.launcher.port=7540... Testing started at 2:29 PM ... Unable to load a Suite class. This could be due to an error in your runpath.

Missing class: BasicActorSpec java.lang.ClassNotFoundException: BasicActorSpec at java.net.URLClassLoader$1.run(URLClassLoader.java:366) at java.net.URLClassLoader$1.run(URLClassLoader.java:355) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:354) at java.lang.ClassLoader.loadClass(ClassLoader.java:424) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308) at java.lang.ClassLoader.loadClass(ClassLoader.java:357) at org.scalatest.tools.Runner$$anonfun$35.apply(Runner.scala:2393) at org.scalatest.tools.Runner$$anonfun$35.apply(Runner.scala:2391) at scala.collection.TraversableLike$$anonfun$filter$1.apply(TraversableLike.scala:264) at scala.collection.immutable.List.foreach(List.scala:318) at scala.collection.TraversableLike$class.filter(TraversableLike.scala:263) at scala.collection.AbstractTraversable.filter(Traversable.scala:105) at org.scalatest.tools.Runner$.doRunRunRunDaDoRunRun(Runner.scala:2391) at org.scalatest.tools.Runner$$anonfun$runOptionallyWithPassFailReporter$2.apply(Runner.scala:1006) at org.scalatest.tools.Runner$$anonfun$runOptionallyWithPassFailReporter$2.apply(Runner.scala:1005) at org.scalatest.tools.Runner$.withClassLoaderAndDispatchReporter(Runner.scala:2659) at org.scalatest.tools.Runner$.runOptionallyWithPassFailReporter(Runner.scala:1005) at org.scalatest.tools.Runner$.run(Runner.scala:845) at org.scalatest.tools.Runner.run(Runner.scala) at org.jetbrains.plugins.scala.testingSupport.scalaTest.ScalaTestRunner.runScalaTest2(ScalaTestRunner.java:144) at org.jetbrains.plugins.scala.testingSupport.scalaTest.ScalaTestRunner.main(ScalaTestRunner.java:35) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)

Process finished with exit code 0

I can't figure out what this means. I've done a lot of searching but can't seem to find an answer. Note that the class the runner is complaining about not finding is the class I'm trying to test/run. The basicTest.scala looks like this:

// Testing specific imports
import org.junit.runner.RunWith
import org.scalatest.junit.JUnitRunner
import org.scalatest.{ShouldMatchers, WordSpecLike, BeforeAndAfterAll}
import akka.testkit.{TestKit, DefaultTimeout, ImplicitSender}
// Actor specific imports
import akka.actor.{ActorRef, Actor, ActorSystem, Props}
// Misc. needed imports
import scala.concurrent.duration._
import com.typesafe.config.ConfigFactory


// In order to run tests in this module you need to use JUnitRunner (as per scalatest.org)
@RunWith(classOf[JUnitRunner])
class BasicActorSpec extends TestKit(ActorSystem("BasicActorSpec", ConfigFactory.parseString(BasicActorSpec.config)))
  with DefaultTimeout with ImplicitSender with WordSpecLike with ShouldMatchers with BeforeAndAfterAll {

  import BasicActorSpec._

  val echoRef = system.actorOf(Props[EchoActor])
  val forwardRef = system.actorOf(Props[ForwardActor])

  override def afterAll {
    shutdown(system)
  }


  /**
   * The actual tests...
   */
  "An EchoActor" should {
    "Respond with the same message it receives" in {
      within(500 millis) {
        echoRef ! "test"
        expectMsg("test")
      }
    }
  }

  "A Forwarding Actor" should {
    "Forward a message it receives" in {
      within(500 millis) {
        forwardRef ! "test"
        expectMsg("test")
      }
    }
  }

}

/**
 * Companion object of test class
 */
object BasicActorSpec {

  val config =
    """
      |akka {
      | loglevel = "Warning"
      |}
    """.stripMargin

  /**
   * Classes of Actors used in testing
   */
  class EchoActor extends Actor {
    def receive = {
      case msg => sender ! msg
    }
  }

  class ForwardActor(next: ActorRef) extends Actor {
    def receive = {
      case msg => next ! msg
    }
  }

}

Any help as to why I am getting this error would be GREATLY appreciated.

Answer 1

Run build the project - It helped me to resolve that issue that could have happened to me when I cleared Cache IDEA :) while trying to tackle another issue

Answer 2

This is how I solved same exception:

--> Right click on your project folder in IDE:

--> Click Add Framework Support
--> Then Check Scala
--> Click OK

Answer 3

My project already had the setup as mentioned by @Rustam Aliyev. Still was getting the same exception. Rebuilding the project did not help either. Quite weird ; but Restarting the IDE helped to solve the issue

Answer 4

I met this issue when I used Gatling

I fix it by replacing gatling-classes to test-classes on File -> Project Structure -> Modules -> Module Name -> Paths -> Test output path

Answer 5

You need to set up the Scala SDK. 1.) Usually, intelliJ will ask you by showing a message on right hand corner of your editor 2.) You can do it by yourself as mentioned on the https://www.jetbrains.com/help/idea/discover-intellij-idea-for-scala.html

Answer 6

In my case, I was missing the Scala facet in my module.

https://blog.jetbrains.com/scala/2010/09/02/project-configuration-explained/

I got rid of the error once I configured module properly.

Answer 7

This issue happened to me recently when I was trying to run tests in an inherited Scala project using IntelliJ IDEA 2018 (Community Edition). Below steps helped me to fix it:

1. File → Project Structure → {Choose specific module} → "Paths" tab → Select "Use module compile output path" → Modify "Test output path" to point to test-classes folder. For example:

   Output path: /home/rustam/IdeaProjects/{project}/{module}/target/scala-2.12/classes
   Test output path: /home/rustam/IdeaProjects/{project}/{module}/target/scala-2.12/test-classes

2. IntelliJ does not like multiple Scala classes defined in one file, so make sure the test class is named the same as the test file and nest other helper classes, which you can refactor later as necessary.

Answer 8

If you are using IntelliJ to run scalatest make sure the class paths are correct. For example:

 /dummyApp 

your build.sbt should look like, name := "dummyApp". If you name it name := "dummy App" you will get errors.

Answer 9

In my case I had in Preferences -> Build, Execution, Deployment -> sbt

Use sbt shell for build and import checkbox enabled

And the test was not in the expected directory src/test but in src/it (integrated test).

Answer 10

I encountered the error when the test class was not part of any package.

Answer 11

I am using the multi maven module and tried all possibilities here but not able to fix this. But for me I closed the complete IntelliJ -> removed .idea folder -> deleted managed projects from recent projects window.-> reimport the project did the job.

Answer 12

This kind of thing keeps happening to me every now and then. All the more concrete suggestions above have merit. Another possibility (which worked this time for me): Edit the run configuration for your tests; click "Use sbt"; run the tests (this should have no problem since it's just using the sbt-shell to run the tests); now unselect "Use sbt" and try it. It worked for me.

Answer 13

Another one in the long list of checks, if you do not use unique test names you get this error without any hint, in a long test suite it is easier to miss.
Failed

test("Check thing 1") {
 class TestClass1 extends MainClass1{
 ... }
test("Check thing 1") {
 class TestClass2 extends MainClass2{
 ... }

Successful

test("Check thing 1") {
 class TestClass1 extends MainClass1{
 ... }
test("Check thing 2") {
 class TestClass2 extends MainClass2{
 ... }

Answer 14

I got the same message on Idea 2021.1. I tried all the ways above but what helped me is running Scala-tests via sbt like this:

sbt "; project nameOfProject; testOnly some.package.SomeTest"

After that I could debug the same tests via Idea.