Update JUnit4 instrumentation to fire test suite events for Bazel

[daniel-mohedano]

What Does This Do

• Introduces proper handling for Bazel's JUnit tests runner suite events by:
  • Removing the previous temporary solution of lazy starting suites.
  • Introduces a new instrumentation for fireTestSuiteStarted and fireTestSuiteFinished methods to unwrap the notifiers and propagate the firing to our tracing listener.

Motivation

Bazel's default JUnit4 configuration for running test suites introduces changes that mess with our instrumentation:

1. Bazel's JUnit entry-point is through BazelTestRunner.main(), which builds a JUnit4Runner (does not inherit org.junit.runner.Runner) and calls run().
2. JUnit4Runner.run() instantiates JUnitCore, registers its run listeners and calls core.run(cancellableRequest).
3. JUnitCore creates a fresh RunNotifier (from now on A) and registers the listeners on it.
4. The request is run with a custom CancellableRunner (extends org.junit.runner.Runner). Its run(A) does currentNotifier = new ThreadSafeRunNotifier(A); delegate.run(currentNotifier);.
5. ThreadSafeRunNotifier extends RunNotifierWrapper extends RunNotifier, so currentNotifier (from now on B) has its own private inherited listeners field.
6. The real runner.run(B) executes.
7. Our instrumentation modifies the call to do B.addListener(tracingListener), but Bs implementation overrides the method to call delegate.addListener(tracingListener); so our listener lands on A.listeners.
8. The real runner fires events such as test suite starts with B.fireTestSuiteStarted(...).
9. The wrapper does not override test suite methods, so it is resolved as RunNotifier.fireTestSuiteStarted(...) invoked with this = B. This iterates over B.listeners, which is empty.
10. The wrapper does forward regular test events with delegate.fireTest...(...) by overriding the methods

All this caused test suite events to be dropped.

Additional Notes

test-environment-trigger: skip

Contributor Checklist

• Format the title according to the contribution guidelines
• Assign the type: and (comp: or inst:) labels in addition to any other useful labels
• Avoid using close, fix, or any linking keywords when referencing an issue
  Use solves instead, and assign the PR milestone to the issue
• Update the CODEOWNERS file on source file addition, migration, or deletion
• Update public documentation with any new configuration flags or behaviors

Jira ticket: [PROJ-IDENT]

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[cit-pr-commenter-54b7da]

Test Environment - sbt-scalatest

Job Status: success

Scenario	Overhead (%)
agent	56.98
agentEvpProxy	56.37

[cit-pr-commenter-54b7da]

Test Environment - nebula-release-plugin

Job Status: success

Scenario	Overhead (%)
agent	37.94
agentless	36.40
agentlessCodeCoverage	43.61
agentlessLineCoverage	76.60

[cit-pr-commenter-54b7da]

Test Environment - netflix-zuul

Job Status: success

Scenario	Overhead (%)
agent	88.39
agentless	81.20
agentlessCodeCoverage	95.83
agentlessLineCoverage	112.65

[cit-pr-commenter-54b7da]

Test Environment - pass4s

Job Status: failed

Scenario	Overhead (%)

[cit-pr-commenter-54b7da]

Test Environment - reactive-streams-jvm

Job Status: success

Scenario	Overhead (%)
agent	21.87
agentless	18.54
agentlessCodeCoverage	19.48
agentlessLineCoverage	29.68

[cit-pr-commenter-54b7da]

Test Environment - sonar-kotlin

Job Status: success

Scenario	Overhead (%)
agent	13.86
agentless	12.42
agentlessCodeCoverage	15.76
agentlessLineCoverage	18.84

[cit-pr-commenter-54b7da]

Test Environment - jolokia

Job Status: success

Scenario	Overhead (%)
agent	94.94
agentless	90.16
agentlessCodeCoverage	97.43
agentlessLineCoverage	99.99

[cit-pr-commenter-54b7da]

Test Environment - okhttp

Job Status: success

Scenario	Overhead (%)
agent	20.51
agentless	19.78
agentlessCodeCoverage	23.38
agentlessLineCoverage	45.82

[cit-pr-commenter-54b7da]

Test Environment - spring_boot

Job Status: success

Scenario	Overhead (%)
agent	16.25
agentless	9.68
agentlessCodeCoverage	12.93
agentlessLineCoverage	33.86

[cit-pr-commenter-54b7da]

Test Environment - sonar-java

Job Status: success

Scenario	Overhead (%)
agent	13.06
agentless	14.07
agentlessCodeCoverage	76.97
agentlessLineCoverage	176.85

[daniel-mohedano]

/merge

[gh-worker-devflow-routing-ef8351]

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2026-05-12 07:20:26 UTC ℹ️ Start processing command /merge

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It will be added to the queue as soon as checks pass and/or get approvals. View in MergeQueue UI.
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2026-05-12 07:49:22 UTC ⚠️ MergeQueue: This merge request was unqueued

daniel.mohedano@datadoghq.com unqueued this merge request

[daniel-mohedano]

/merge -c

[gh-worker-devflow-routing-ef8351]

View all feedbacks in Devflow UI.

2026-05-12 07:49:16 UTC ℹ️ Start processing command /merge -c

[daniel-mohedano]

/merge

[gh-worker-devflow-routing-ef8351]

View all feedbacks in Devflow UI.

2026-05-12 09:39:43 UTC ℹ️ Start processing command /merge

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2026-05-12 09:39:49 UTC ℹ️ MergeQueue: pull request added to the queue

The expected merge time in master is approximately 1h (p90).

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2026-05-12 11:02:20 UTC ℹ️ MergeQueue: This merge request was merged