Play 2.3 FakeApplication mode not setting in test?

I'm using play 2.3 and have some configuration in my GlobalSettings that change based on the mode of the application. So I have something like this:

object Global extends GlobalSettings {
    override def onLoadConfig(config: Configuration, path: java.io.File, classloader: ClassLoader, mode: Mode.Mode) = {
        println(mode)
        val customConfig = //Based on mode.*
        config ++ configuration ++ Configuration(ConfigFactory.parseMap(customConfig))
    }
}

And then am trying to write tests to ensure that this behavior works:

class MyTest extends PlaySpec {

    val testApp = FakeApplication(
        additionalConfiguration = Map(
            //SomeSettings And Stuff
            "logger.application" -> "WARN",
            "logger.root" -> "WARN"
        )
    )

    val devApp = new FakeApplication(
        additionalConfiguration = Map(
            //SomeSettings And Stuff
            "logger.application" -> "WARN",
            "logger.root" -> "WARN"
        )
    ) {
        override val mode = Mode.Dev
    }

    val prodApp = new FakeApplication(
        additionalConfiguration = Map(
            //SomeSettings And Stuff
            "logger.application" -> "WARN",
            "logger.root" -> "WARN"
        )
    ) {
        override val mode = Mode.Prod
    }

    "ThisNonWorkingTestOfMine" must {

        "when running application in test mode have config.thing = false" in running(testApp) {
            assertResult(Mode.Test)(testApp.mode)
            assertResult(false)(testApp.configuration.getBoolean("config.thing").get)
        }

        "when running application in dev mode have config.thing = false" in running(devApp) {
            assertResult(Mode.Dev)(devApp.mode)
            assertResult(false)(devApp.configuration.getBoolean("config.thing").get)
        }

        "when running application in prod mode have config.thing = true" in running(prodApp) {
            assertResult(Mode.Prod)(prodApp.mode)
            assertResult(true)(prodApp.configuration.getBoolean("config.thing").get)
        }
    }

}

And when I run these tests I see something a bit odd from my handy println:

Test
null
null
[info] MyTest:
[info] ThisNonWorkingTestOfMine
[info] play - Starting application default Akka system.
[info] play - Shutdown application default Akka system.
[info] - must when running application in test mode have config.thing = false
[info] play - Application started (Dev)
[info] - must when running application in dev mode have config.thing = false
[info] play - Application started (Prod)
[info] - must when running application in prod mode have config.thing = true *** FAILED ***
[info]   Expected true, but got false (MyTest.scala:64)
[info] ScalaTest

How do I properly set the mode of the FakeApplication in Play 2.3? The way I have it now is based on a page from Mastering Play but clearly that isn't the way to go when using onLoadConfig it seems