Unit testing for PR and branch

We are using SonarQube developer edition for our project hosted in GitHub enterprise. So far, we are widely using Sonarqube for our PR and branch. But, we have a challenge that the Unit testing need to be run twice: One in the PR phase and one in the branch merge. In our quality gate, we define the testing coverage is one criterial so we can not skip the testing phase. The UT takes several minutes which causes some latency. Any suggestion from expert here?