NIFI-15432 Add system tests to code coverage workflow

[pvillard31]

Summary

NIFI-15432 Add system tests to code coverage workflow

• Add system-tests job to collect coverage from spawned NiFi instances
• Configure JaCoCo agent injection via JACOCO_AGENT_PATH environment variable
• Modify SpawnedStandaloneNiFiInstanceFactory to configure JaCoCo agent in bootstrap.conf
• Collect and merge jacoco.exec files from system tests and stateless tests
• Convert merged coverage data to XML format for Codecov upload
• Dynamically extract module list from nifi-code-coverage/pom.xml
• Add nifi-registry-integration-tests profile to integration tests job

When doing testing in my fork, it's getting us to 60%+ of coverage.
https://app.codecov.io/github/pvillard31/nifi/commit/ec991a105874edbd925a95bb6eea9c2d060561e1/tree

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• Apache NiFi Jira issue created

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• Build completed using ./mvnw clean install -P contrib-check
  • JDK 21
  • JDK 25

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[exceptionfactory]

Thanks for working on this substantive improvement to code coverage tracking @pvillard31. The general approach of passing the JaCoCo agent handling through the system tests looks like a good strategy.

On initial review, my primary concern is the extensive amount of scripting in the code coverage workflow, in particular the complex sed and grep commands. At minimum, extracting this logic to an external script would support testing and maintenance. However, it does make me wonder if there are other options with potentially less scripting involved.

[pvillard31]

Thanks for the feedback @exceptionfactory - I extracted the scripting into an external dedicated script file. Given the nature of the system tests and how they work / are executed, I didn't find any other (better) option during my testing.

[exceptionfactory]

Thanks for moving the script to a separate file @pvillard31, the approach looks good! +1 merging