This PR fixes a critical JUnit 5 compatibility issue where TestPipeline.run() would throw an IllegalStateException about missing @Rule annotation even when using the proper TestPipelineExtension for JUnit 5.

[chennu2020]

Issue

When using Apache Beam's TestPipelineExtension with JUnit 5, tests would fail with:

java.lang.IllegalStateException: Is your TestPipeline declaration missing a @Rule annotation? 
Usage: @Rule public final transient TestPipeline pipeline = TestPipeline.create();

Root Cause Analysis

1. TestPipeline Internal Validation: The TestPipeline class had internal validation logic that expected the @Rule annotation to be present, even when used in JUnit 5 context through TestPipelineExtension.

2. Enforcement Coordination Issue: The TestPipelineExtension was creating duplicate enforcement mechanisms that conflicted with TestPipeline's internal enforcement, leading to coordination problems.

3. JUnit 5 Context Detection: TestPipeline lacked proper detection of JUnit 5 execution context, causing it to apply JUnit 4-specific validation rules inappropriately.

Solution Implementation

1. Enhanced TestPipeline.java

File: sdks/java/core/src/main/java/org/apache/beam/sdk/testing/TestPipeline.java

Key Changes:

• JUnit 5 Context Detection: Added logic to detect JUnit 5 execution context by inspecting the call stack for JUnit 5-specific classes
• Conditional Enforcement: Modified run() method to set default enforcement when running in JUnit 5 context
• Backward Compatibility: Maintained full compatibility with existing JUnit 4 usage patterns

// Enhanced run() method with JUnit 5 detection
@Override
public PipelineResult run() {
  // Detect JUnit 5 context and set enforcement if needed
  if (enforcement.get() == null && isJUnit5Context()) {
    setDeducedEnforcementLevel();
  }
  return super.run();
}

private boolean isJUnit5Context() {
  // Stack trace inspection to detect JUnit 5 execution
  return Arrays.stream(Thread.currentThread().getStackTrace())
      .anyMatch(frame -> frame.getClassName().startsWith("org.junit.jupiter"));
}

2. Improved TestPipelineExtension.java

File: sdks/java/testing/junit/src/main/java/org/apache/beam/sdk/testing/TestPipelineExtension.java

Key Changes:

• Enforcement Initialization: Enabled enforcement in constructors with enableAbandonedNodeEnforcement(true)
• Removed Duplicate Enforcement: Eliminated duplicate enforcement creation in setDeducedEnforcementLevel() to prevent conflicts
• Simplified Coordination: Let TestPipeline handle its own enforcement mechanism instead of creating separate extension enforcement

// Simplified enforcement coordination
private void setDeducedEnforcementLevel() {
  // Let TestPipeline handle enforcement - avoid duplication
  if (testPipeline.enforcement.get() == null) {
    testPipeline.setDeducedEnforcementLevel();
  }
}

3. Comprehensive Test Coverage

Files:

• TestPipelineJUnit5CompatibilityTest.java - New comprehensive JUnit 5 compatibility tests
• TestPipelineJUnit4And5InteroperabilityTest.java - Interoperability validation tests

Test Coverage:

• JUnit 5 pipeline injection and execution
• Enforcement coordination between TestPipeline and TestPipelineExtension
• Pipeline execution tracking and validation
• Empty pipeline handling
• Multiple pipeline operations
• Pipeline options integration
• PAssert integration
• Error handling and propagation
• JUnit 4/5 interoperability

---

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[gemini-code-assist]

Summary of Changes

Hello @chennu2020, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a long-standing compatibility issue preventing Apache Beam's "TestPipeline" from working seamlessly with JUnit 5's "TestPipelineExtension". The core problem stemmed from "TestPipeline"'s internal validation expecting JUnit 4's "@rule" annotation even in a JUnit 5 context. The solution involves enhancing "TestPipeline" to intelligently detect its execution environment and adapt its enforcement logic, while also refining "TestPipelineExtension" to better coordinate with "TestPipeline"'s internal mechanisms. This ensures that developers can now use "TestPipeline" with JUnit 5 without encountering "IllegalStateException"s, maintaining full backward compatibility with JUnit 4, and significantly improving the testing experience for Beam users.

Highlights

• JUnit 5 Compatibility: Resolves a critical "IllegalStateException" in "TestPipeline.run()" when used with JUnit 5's "TestPipelineExtension", which previously incorrectly demanded a "@rule" annotation.
• Conditional Enforcement in TestPipeline: "TestPipeline.java" now includes logic to detect JUnit 5 execution contexts by inspecting the call stack, allowing it to conditionally apply enforcement mechanisms and bypass JUnit 4-specific "@rule" validation.
• Streamlined TestPipelineExtension: "TestPipelineExtension.java" has been updated to initialize enforcement directly in its constructors and "getOrCreateTestPipeline" method, and to eliminate redundant enforcement creation, preventing conflicts and simplifying coordination with "TestPipeline".
• Enhanced Test Coverage: New comprehensive test files, "TestPipelineJUnit5CompatibilityTest.java" and "TestPipelineJUnit4And5InteroperabilityTest.java", have been added to validate JUnit 5 compatibility, ensure backward compatibility with JUnit 4, and confirm proper enforcement coordination and pipeline execution tracking.

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[github-actions]

Checks are failing. Will not request review until checks are succeeding. If you'd like to override that behavior, comment assign set of reviewers

[Abacn]

This looks like an ad-hoc fix. There should be a cleaner way to do this (than bump stack trace and check class name). Let me also do some experiments.

[Abacn]

opened #36258

[chennu2020]

Thank you