title: ScalaTest runner + FunSuite + tag: can't get `-n` and `-l` to include/exclude tag?
body: <p>The ScalaTest runner is supposed to support including or excluding tests by tag, but I can't get it to work. What am I doing wrong? Details follow.</p>
  
  <p>in an otherwise empty directory, given build.sbt:</p>
  
  <pre><code>libraryDependencies += "org.scalatest" %% "scalatest" % "2.1.0" % "test"
  </code></pre>
  
  <p>and src/test/scala/Test.scala:</p>
  
  <pre><code>class Test extends org.scalatest.FunSuite {
    test("fast") {
      assertResult(4)(2 + 2) }
    test("slow", org.scalatest.tagobjects.Slow) {
      assertResult(40)(20 + 20) }
  }
  </code></pre>
  
  <p>then:</p>
  
  <pre><code>% sbt
  [info] Set current project to bug (in build file:/Users/tisue/bug/)
  &gt; show sbtVersion
  [info] 0.13.1
  &gt; test
  [info] Compiling 1 Scala source to /Users/tisue/bug/target/scala-2.10/test-classes...
  [info] Test:
  [info] - fast
  [info] - slow
  [info] Run completed in 192 milliseconds.
  [info] Total number of tests run: 2
  [info] Suites: completed 1, aborted 0
  [info] Tests: succeeded 2, failed 0, canceled 0, ignored 0, pending 0
  [info] All tests passed.
  [success] Total time: 3 s, completed Mar 15, 2014 12:25:06 PM
  </code></pre>
  
  <p>so far so good. but now:</p>
  
  <pre><code>&gt; test-only Test -- -l org.scalatest.tagobjects.Slow
  [info] Test:
  [info] - fast
  [info] - slow
  [info] Run completed in 108 milliseconds.
  [info] Total number of tests run: 2
  [info] Suites: completed 1, aborted 0
  [info] Tests: succeeded 2, failed 0, canceled 0, ignored 0, pending 0
  [info] All tests passed.
  [success] Total time: 0 s, completed Mar 15, 2014 12:25:39 PM
  &gt; test-only Test -- -n org.scalatest.tagobjects.Slow
  [info] Test:
  [info] Run completed in 93 milliseconds.
  [info] Total number of tests run: 0
  [info] Suites: completed 1, aborted 0
  [info] Tests: succeeded 0, failed 0, canceled 0, ignored 0, pending 0
  [info] No tests were executed.
  [success] Total time: 0 s, completed Mar 15, 2014 12:25:42 PM
  </code></pre>
  
  <p>using <code>-l</code> to exclude the tag didn't exclude anything, and using <code>-n</code> to include the tag didn't include anything.</p>
  
  <p>The problem isn't specific to sbt/ScalaTest integration, because it also fails if I run the runner directly:</p>
  
  <pre><code>&gt; test:run-main org.scalatest.tools.Runner -o -R target/scala-2.10/test-classes -l org.scalatest.tagobjects.Slow
  [info] Running org.scalatest.tools.Runner -o -R target/scala-2.10/test-classes -l org.scalatest.tagobjects.Slow
  Discovery starting.
  Discovery completed in 52 milliseconds.
  Run starting. Expected test count is: 2
  Test:
  - fast
  - slow
  Run completed in 96 milliseconds.
  Total number of tests run: 2
  Suites: completed 2, aborted 0
  Tests: succeeded 2, failed 0, canceled 0, ignored 0, pending 0
  All tests passed.
  
  Exception: sbt.TrapExitSecurityException thrown from the UncaughtExceptionHandler in thread "ScalaTest-main"
  [success] Total time: 0 s, completed Mar 15, 2014 12:30:14 PM
  &gt; test:run-main org.scalatest.tools.Runner -o -R target/scala-2.10/test-classes -n org.scalatest.tagobjects.Slow
  [info] Running org.scalatest.tools.Runner -o -R target/scala-2.10/test-classes -n org.scalatest.tagobjects.Slow
  Discovery starting.
  Discovery completed in 51 milliseconds.
  Run starting. Expected test count is: 0
  Test:
  Run completed in 86 milliseconds.
  Total number of tests run: 0
  Suites: completed 2, aborted 0
  Tests: succeeded 0, failed 0, canceled 0, ignored 0, pending 0
  No tests were executed.
  
  Exception: sbt.TrapExitSecurityException thrown from the UncaughtExceptionHandler in thread "ScalaTest-main"
  [success] Total time: 0 s, completed Mar 15, 2014 12:30:18 PM
  </code></pre>
  
  <p>What am I doing wrong?</p>