Pass actual TestPlatform and OperatingSystem values to Suite.

lib/src/backend/invoker.dart

Index: lib/src/backend/invoker.dart
diff --git a/lib/src/backend/invoker.dart b/lib/src/backend/invoker.dart
index fce4089aeb8d63f0d43fdc5486ac1a9f22c871f1..da978ba67aa09edaecd4bd9a25bc3d190e38f563 100644
--- a/lib/src/backend/invoker.dart
+++ b/lib/src/backend/invoker.dart
@@ -45,6 +45,7 @@ class LocalTest implements Test {
   }
 
   Test change({String name, Metadata metadata}) {
+    if (name == name && metadata == this.metadata) return this;
     if (name == null) name = this.name;
     if (metadata == null) metadata = this.metadata;
     return new LocalTest(name, metadata, _body, tearDown: _tearDown);