When the build result is "unstable", the Gitea plugin is sending a status of "failure" back to Gitea. It also sends the hard-coded and misleading description "This commit has test failures".

The expected status in this case is "warning" and the description should be something along the lines of "This commit is unstable".

https://github.com/jenkinsci/gitea-plugin/blob/master/src/main/java/org/jenkinsci/plugin/gitea/GiteaNotifier.java#L105

This section of code appears to have been copied from the Bitbucket plugin, which also has a similar issue, JENKINS-46250.