Improve test strategy on claude.md (#11270)

Improve test strategy on claude.md

Update .claude/CLAUDE.md

Co-authored-by: Bruce Bujon <PerfectSlayer@users.noreply.github.com>

Update AGENTS.md

Co-authored-by: Bruce Bujon <PerfectSlayer@users.noreply.github.com>

suggestion

Co-authored-by: devflow.devflow-routing-intake <devflow.devflow-routing-intake@kubernetes.us1.ddbuild.io>

Author: amarziali

.claude/CLAUDE.md

@@ -3,3 +3,4 @@
 ## Claude Code workflow
 
 - Before creating a pull request, run `/techdebt` to check for technical debt, code duplication, and unnecessary complexity in the branch changes.
+- Always write new unit tests using JUnit 5 and Java. If the target test file is `.groovy`, run the `/migrate-groovy-to-java` skill on it first.

AGENTS.md

@@ -58,7 +58,7 @@ docs/                     Developer documentation (see below)
 - **Formatting**: google-java-format enforced via Spotless. Run `./gradlew spotlessApply` before committing.
 - **Instrumentation layout**: `dd-java-agent/instrumentation/{framework}/{framework}-{minVersion}/`
 - **Instrumentation pattern**: Type matching → Method matching → Advice class (bytecode advice, not AOP)
-- **Test frameworks**: JUnit 5 (preferred for unit tests), Spock 2 (for complex scenarios needing Groovy)
+- **Test frameworks**: Always use JUnit 5. **Do not write new Groovy / Spock tests** and migrate the existing one to JUnit 5 if it is written in Groovy.
 - **Forked tests**: Use `ForkedTest` suffix when tests need a separate JVM
 - **Flaky tests**: Annotate with `@Flaky` — they are skipped in CI by default