Add a function to parse metadata into a usable object.

test/runner/parse_metadata_test.dart

+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// 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 'dart:io';
+
+import 'package:path/path.dart' as p;
+import 'package:unittest/unittest.dart';
+import 'package:unittest/src/runner/parse_metadata.dart';
+
+String _sandbox;
+String _path;
+
+void main() {
+  setUp(() {
+    _sandbox = Directory.systemTemp.createTempSync('unittest_').path;
+    _path = p.join(_sandbox, "test.dart");
+  });
+
+  tearDown(() {
+    new Directory(_sandbox).deleteSync(recursive: true);
+  });
+
+  test("returns empty metadata for an empty file", () {
+    new File(_path).writeAsStringSync("");
+    var metadata = parseMetadata(_path);
+    expect(metadata.testOn, isNull);
+  });
+
+  test("ignores irrelevant annotations", () {
+    new File(_path).writeAsStringSync("@Fblthp\n@Fblthp.foo\nlibrary foo;");
+    var metadata = parseMetadata(_path);
+    expect(metadata.testOn, isNull);
+  });
+
+  test("parses a valid annotation", () {
+    new File(_path).writeAsStringSync("@TestOn('foo')\nlibrary foo;");
+    var metadata = parseMetadata(_path);
+    expect(metadata.testOn, equals("foo"));
+  });
+
+  test("parses a prefixed annotation", () {
+    new File(_path).writeAsStringSync(
+        "@foo.TestOn('foo')\n"
+        "import 'package:unittest/unittest.dart' as foo;");
+    var metadata = parseMetadata(_path);
+    expect(metadata.testOn, equals("foo"));
+  });
+
+  test("ignores a constructor named TestOn", () {
+    new File(_path).writeAsStringSync("@foo.TestOn('foo')\nlibrary foo;");
+    var metadata = parseMetadata(_path);
+    expect(metadata.testOn, isNull);
+  });
+
+  group("throws an error for", () {
+    test("a named constructor", () {
+      new File(_path).writeAsStringSync("@TestOn.name('foo')\nlibrary foo;");
+      expect(() => parseMetadata(_path), throwsFormatException);
+    });
+
+    test("no argument list", () {
+      new File(_path).writeAsStringSync("@TestOn\nlibrary foo;");
+      expect(() => parseMetadata(_path), throwsFormatException);
+    });
+
+    test("an empty argument list", () {
+      new File(_path).writeAsStringSync("@TestOn()\nlibrary foo;");
+      expect(() => parseMetadata(_path), throwsFormatException);
+    });
+
+    test("a named argument", () {
+      new File(_path).writeAsStringSync(
+          "@TestOn(expression: 'foo')\nlibrary foo;");
+      expect(() => parseMetadata(_path), throwsFormatException);
+    });
+
+    test("multiple arguments", () {
+      new File(_path).writeAsStringSync("@TestOn('foo', 'bar')\nlibrary foo;");
+      expect(() => parseMetadata(_path), throwsFormatException);
+    });
+
+    test("a non-string argument", () {
+      new File(_path).writeAsStringSync("@TestOn(123)\nlibrary foo;");
+      expect(() => parseMetadata(_path), throwsFormatException);
+    });
+
+    test("multiple @TestOns", () {
+      new File(_path).writeAsStringSync(
+          "@TestOn('foo')\n@TestOn('bar')\nlibrary foo;");
+      expect(() => parseMetadata(_path), throwsFormatException);
+    });
+  });
+}