Running Groovy test cases with JUnit 5 - groovy

Question

Maybe this is very simple, but I couldn't find any examples on the web:
I'd like to use JUnit 5 to run a unit test implemented as a Groovy class. My current setup seems to launch JUnit 5, but fail to detect the test case. IntelliJ recognizes the test, but fails to run it. If I add a Java unit test, it is launched correctly.
Here's what I have now:
Project structure
src
main
groovy
# production code
test
groovy
UnitTest.groovy
build.gradle
...
build.gradle
plugins {
id 'groovy'
}
dependencies {
compile localGroovy()
testImplementation 'org.junit.jupiter:junit-jupiter-api:5.1.1'
testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.1.1'
}
test {
useJUnitPlatform()
}
UnitTest.groovy
import org.junit.jupiter.api.Test
class UnitTest {
#Test
def shouldDoStuff() {
throw new RuntimeException()
}
}
I'm using Gradle 4.10.
Any ideas?

Answer 1

JUnit requires all testing method to use return type void. Groovy's def keyword is compiled to an Object type, so your method compiles to something like this in Java:
import org.junit.jupiter.api.Test
public class UnitTest {
#Test
Object shouldDoStuff() {
throw new RuntimeException();
}
}
If you try this out as a Java test, it won't find the test case neither. The solution is very simple - replace def with void and your Groovy
test case will be executed correctly.
src/test/groovy/UnitTest.groovy
import org.junit.jupiter.api.Test
class UnitTest {
#Test
void shouldDoStuff() {
throw new RuntimeException()
}
}
Demo: