Maven/Gradle pin test sources to src/test/<lang>/ — java, kotlin, scala, groovy all share the layout. Real route handlers never live there, but Quarkus, Micronaut, Spring, Javalin, JAX-RS and friends routinely declare inline controllers under src/test/java/... to exercise the framework. The path layout is part of the build tool's contract so the prefix check is unambiguous.

Also covers Maven's archetype source-roots (src/it/, integration-test convention used by some Quarkus extensions and Apache projects) which sit alongside src/test/.