Kotlin projects should automatically depend on org.jetbrains.kotlin:kotlin-test-junit5

[darioseidl]

To write JUnit tests in Kotlin it is recommended to include testImplementation(kotlin("test")), i.e. the kotlin-test dependency.

Tests work without that, but fallback to the default implmentation for assertions instead of using the JUnit implementation, as I learned here:
https://youtrack.jetbrains.com/issue/KT-50260

Normally, kotlin-test delegates assertions like equality to the assertion API of an underlying testing framework, and the default implementation is used only as a last resort. To enable such delegation on JVM you need to ensure that you have a dependency on either kotlin-test-junit, or kotlin-test-junit5, or kotlin-test-testng.

Note that in Gradle, the Kotlin plugin can determine automatically which flavor of kotlin-test dependency to use based on the test runner used in a project.

I was surprised that I had to add testImplementation(kotlin("test")) myself, and it wasn't added in Spring initializer projects. What do you think?

[wilkinsona]

Thanks for the suggestion, @darioseidl. We'll want to do the same for a Kotlin project built with Maven. AIUI, kotlin("test") maps to org.jetbrains.kotlin:kotlin-test-junit5 when using JUnit 5. It may be easier to add this dependency directly as that'll work with either build system.