Gradle, IntelliJ and ScalaTest plugin: suddenly broken

Question

This is very puzzling. I have a multi module polyglot JVM project built using Gradle. I have a few java modules and a couple scala modules. The scala module uses ScalaTest as the test framework. I set up the Gradle to use the scalatest plugin to run tests. I had the whole thing running like a charm in IntelliJ for about a month (using the Gradle idea plugin). Now all of a sudden the ScalaTest specs won't run from the IDE anymore with the following error:

Unable to load a Suite class. This could be due to an error in your runpath. Missing class: com.mypackage.MySpec

Does anybody know what's going on? I am not sure what has changed since the first time I set up my build file that might have messed this up. This is really frustrating. Ideas?

EDIT: Apparently my junit tests won't run either. Looks like the compiled classes aren't on the classpath used by Intellij. This is what I get if I try to run a JUnit test case:

Class not found: "com.mypackage.MyUnitTests"

Answer 1

Chances are that since this is a multi-language project IntelliJ can't tell which are the source folders. Check under Project Structure > Modules (each of your module) and ensure Sources and Tests dirs are correctly marked.

Answer 2

Figured it out. I was messing with my IntelliJ configuration files after this blog post and I accidentally messed up my project output folder (in the updateBuildOutputFolderForGradle function) so that IntelliJ wasn't able to find the classes at runtime.