Add tests for simple packages scenarios

tests/standalone/package/scenarios/both_dir_and_file/prefers_packages_file_test.dart

Index: tests/standalone/package/scenarios/both_dir_and_file/prefers_packages_file_test.dart
diff --git a/tests/language/issue13179_test.dart b/tests/standalone/package/scenarios/both_dir_and_file/prefers_packages_file_test.dart
similarity index 54%
copy from tests/language/issue13179_test.dart
copy to tests/standalone/package/scenarios/both_dir_and_file/prefers_packages_file_test.dart
index 0439ceab895f5925234763b90cb323007bc19b14..32251bc2b4d9df4e0b40ca69229163b8dd6bed0a 100644
--- a/tests/language/issue13179_test.dart
+++ b/tests/standalone/package/scenarios/both_dir_and_file/prefers_packages_file_test.dart
@@ -2,18 +2,14 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import "package:expect/expect.dart";
+// PackageRoot=none
 
-int count = 0;
+library prefers_packages_file_test;
 
-void f([void f([x]) = f]) {
-  count++;
-  if (f != null) {
-    f(null);
-  }
-}
+import 'package:foo/foo.dart' as foo;
 
 main() {
-  f();
-  Expect.equals(2, count);
-}
+  if (foo.bar != 'good') {
+    throw new Exception('package "foo" was not resolved correctly');
+  }
+}