feature: tag tests; choose tags on command line

test/backend/declarer_test.dart

Index: test/backend/declarer_test.dart
diff --git a/test/backend/declarer_test.dart b/test/backend/declarer_test.dart
index 39fc3abc5cb21017f1aa2ecdcc07eaf84e500728..8671f575f5ab316461aafcea53b01ed618a726da 100644
--- a/test/backend/declarer_test.dart
+++ b/test/backend/declarer_test.dart
@@ -48,6 +48,27 @@ void main() {
       expect(tests[1].name, equals("description 2"));
       expect(tests[2].name, equals("description 3"));
     });
+
+    test("declares a test with tags", () {
+      var tests = declare(() {
+        test("tags as String", () {}, tags: "a");
+        test("tags as List", () {}, tags: ["a", "b"]);
+        test("tags as null", () {}, tags: null);
+      });
+
+      expect(tests, hasLength(3));
+      expect(tests[0].metadata.tags, unorderedEquals(["a"]));
+      expect(tests[1].metadata.tags, unorderedEquals(["a", "b"]));
+      expect(tests[2].metadata.tags, isEmpty);
+    });
+
+    test("throws on invalid tags", () {
+      expect(() {
+        declare(() {
+          test("a", () {}, tags: 1);
+        });
+      }, throwsArgumentError);
+    });
   });
 
   group(".setUp()", () {
@@ -414,6 +435,32 @@ void main() {
 
         return _runTest(entries.single.entries.single);
       });
+
+      test("inherits group's tags", () {
+        var tests = declare(() {
+          group("outer", () {
+            group("inner", () {
+              test("with tags", () {}, tags: "d");
+            }, tags: ["b", "c"]);
+          }, tags: "a");
+        });
+
+        var outerGroup = tests.single;
+        var innerGroup = outerGroup.entries.single;
+        var testWithTags = innerGroup.entries.single;
+        expect(outerGroup.metadata.tags, unorderedEquals(["a"]));
+        expect(innerGroup.metadata.tags, unorderedEquals(["a", "b", "c"]));
+        expect(testWithTags.metadata.tags,
+            unorderedEquals(["a", "b", "c", "d"]));
+      });
+
+      test("throws on invalid tags", () {
+        expect(() {
+          declare(() {
+            group("a", () {}, tags: 1);
+          });
+        }, throwsArgumentError);
+      });
     });
 
     group(".tearDown()", () {