$ copy-file changes/RunSuccess.scala src/main/scala/Run.scala
[success]
> run
[success]

# an exception in the main thread should be a nonzero exit code
$ copy-file changes/RunFailureMain.scala src/main/scala/Run.scala
[success]
> run
[failure]

# an exception in a non-main thread should still be exit code 0
$ copy-file changes/ThreadRunError.scala src/main/scala/Run.scala
[success]
> run
[success]
