Add a --reporter flag and expose the expanded reporter.

test/runner/compact_reporter_test.dart

Index: test/runner/compact_reporter_test.dart
diff --git a/test/runner/compact_reporter_test.dart b/test/runner/compact_reporter_test.dart
index 4650b9fcc35e49382e7c40339ed2c42852a127d8..a03862ec280a374269ef81faf13cbc94bc78f1a5 100644
--- a/test/runner/compact_reporter_test.dart
+++ b/test/runner/compact_reporter_test.dart
@@ -16,7 +16,8 @@ void main() {
   test("reports when no tests are run", () {
     return withTempDir((path) {
       new File(p.join(path, "test.dart")).writeAsStringSync("void main() {}");
-      var result = runTest(["test.dart"], workingDirectory: path);
+      var result = runTest(["-r", "compact", "test.dart"],
+          workingDirectory: path);
       expect(result.stdout, equals("No tests ran.\n"));
     });
   });
@@ -332,8 +333,10 @@ $tests
   expect(withTempDir((path) {
     new File(p.join(path, "test.dart")).writeAsStringSync(dart);
     if (args == null) args = [];
-    args = args.toList()..add("test.dart");
-    args.add("--concurrency=$concurrency");
+    args = args.toList()
+      ..add("test.dart")
+      ..add("--concurrency=$concurrency")
+      ..add("--reporter=compact");
     var result = runTest(args, workingDirectory: path);
 
     // Convert CRs into newlines, remove excess trailing whitespace, and trim