I know that there are no public API in junit, there are no lib packages that distinguisce what is APIs and what is internal. Anyway xUnit since long time rely on junit-plugin to parse gathered reports and provide a UI report.
Due to recent issues that happens in parallel stage or build steps I need the merge method of TestResultAction is being exposed as public or I'm not able to perform any strategies based only on a specific result gathered by a build step instead of the total registered till now