How to change the default setting '-DskipTests=true' during Heroku deployment?

I am trying to deploy a Java project from Beanstalk using Heroku. But during the deployment process, the tests are skipped by default. I am aware that the default settings for Dskiptests is true. Is it possible to run tests using Heroku? Where do I change the settings to overwrite the default settings. Here is how the build is started by default:

output -----> Java app detected

output -----> Installing OpenJDK 1.8... done

output -----> Executing: mvn -B -DskipTests=true clean install