Add the ability to run test suites in parallel.

test/runner/runner_test.dart

Index: test/runner/runner_test.dart
diff --git a/test/runner/runner_test.dart b/test/runner/runner_test.dart
index 0d59eaf873c4bf4867aacaec44cc389c64490253..77edf6d33ac71d208653a7d98499175083e966e7 100644
--- a/test/runner/runner_test.dart
+++ b/test/runner/runner_test.dart
@@ -38,17 +38,20 @@ void main() {
 final _usage = """
 Usage: pub run test:test [files or directories...]
 
--h, --help                Shows this usage information.
--n, --name                A substring of the name of the test to run.
-                          Regular expression syntax is supported.
+-h, --help                     Shows this usage information.
+-n, --name                     A substring of the name of the test to run.
+                               Regular expression syntax is supported.
 
--N, --plain-name          A plain-text substring of the name of the test to run.
--p, --platform            The platform(s) on which to run the tests.
-                          [vm (default), chrome]
+-N, --plain-name               A plain-text substring of the name of the test to run.
+-p, --platform                 The platform(s) on which to run the tests.
+                               [vm (default), chrome]
 
-    --pub-serve=<port>    The port of a pub serve instance serving "test/".
-    --[no-]color          Whether to use terminal colors.
-                          (auto-detected by default)
+-j, --concurrency=<threads>    The number of concurrent test suites run.
+                               (defaults to 6)

[kevmoo, 2015/04/06 23:38:36]

not all of us have 12 procs :-)

[nweiz, 2015/04/07 00:15:05]

Good catch! Fixed.

+
+    --pub-serve=<port>         The port of a pub serve instance serving "test/".
+    --[no-]color               Whether to use terminal colors.
+                               (auto-detected by default)
 """;
 
 void main() {