Culprit: AbstractTestResultAction/summary.jelly#L29-L39 and usage in AbstractTestResultAction/summary.jelly#L79

Reproduction steps:

• Install JUnit or clone https://github.com/jenkinsci/junit-plugin and then mvn hpi:run
• Create a freestyle job
• Add a post-build "Publish JUnit test result report"
• Add "report.xml" as "Test report XMLs".
• Save + run the job once
• Then put in the workspace the content copy-pasted of report_multiple_failure.xml inside report.xml.
• Run the job once.
• From the build page, you will see the "Show all failed tests >>>"

Screenshot attached about when the feature is displayed.

Proposal

• Move the showFailures method to an external file.
• In the same external file, add a listener on the anchor onclick event. Be careful, the id "showLink" is perhaps too generic (could be present on other elements in the same page. Adding a className like "showFailuresLink" and using it as selector could be a good idea.
• You can find such approach illustrated in https://github.com/jenkinsci/jenkins/pull/5786

Testing notes

• Ensure to reproduce the feature before any change
• Ensure that you reproduce the feature after you have made the change