refactor and cleanup code completion

pkg/analysis_services/test/completion/completion_manager_test.dart

+// Copyright (c) 2014, 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.
+
+library test.services.completion.manager;
+
+import 'package:analysis_services/completion/completion_manager.dart';
+import 'package:analysis_services/src/completion/dart_completion_manager.dart';
+import 'package:analysis_testing/abstract_context.dart';
+import 'package:analysis_testing/reflective_tests.dart';
+import 'package:analyzer/src/generated/source.dart';
+import 'package:unittest/unittest.dart';
+
+main() {
+  groupSep = ' | ';
+  runReflectiveTests(CompletionManagerTest);
+}
+
+@ReflectiveTestCase()
+class CompletionManagerTest extends AbstractContextTest {
+
+  test_dart() {
+    Source source = addSource('/does/not/exist.dart', '');
+    var manager = CompletionManager.create(context, source, 0, null);
+    expect(manager.runtimeType, DartCompletionManager);
+  }
+
+  test_html() {
+    Source source = addSource('/does/not/exist.html', '');
+    var manager = CompletionManager.create(context, source, 0, null);
+    expect(manager.runtimeType, NoOpCompletionManager);
+  }
+
+  test_null_context() {
+    Source source = addSource('/does/not/exist.dart', '');
+    var manager = CompletionManager.create(null, source, 0, null);
+    expect(manager.runtimeType, NoOpCompletionManager);
+  }
+
+  test_other() {
+    Source source = addSource('/does/not/exist.foo', '');
+    var manager = CompletionManager.create(context, source, 0, null);
+    expect(manager.runtimeType, NoOpCompletionManager);
+  }
+}