Testing with OneBrowserPerSuite, but unable to start TestServer with specified http and https port

I am using Play 2.7.3 and writing functional test using ScalaTest extends OneBrowserPerSuite, but the TestServer was started each time with a random port. I need to start the TestServer in specified ports defined, e.g. 9000 for http and 9443 for https. However, I didn’t see how to do this. . Based on this document, I tried setting System property ‘testserver.port’, but it doesn’t work . https://www.playframework.com/documentation/2.7.x/ScalaFunctionalTestingWithScalaTest System.setProperty(“testserver.port”, “9000”)