Play 2.3: How to set configuration file in Test?

Test (activator test) always uses application.conf. There is a solution in another post How do I specify a config file with sbt 0.12.2 for sbt test? but it is in Build.scala. This file is not available in play 2.3 I tried to put javaOptions in Test += "-Dconfig.file=conf/local.conf" in build.sbt but it does not work.