add test for ModalBarrier

packages/flutter/test/widget/modal_barrier_test.dart

+// Copyright 2016 The Chromium Authors. 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:flutter_test/flutter_test.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter/widgets.dart';
+import 'package:test/test.dart';
+
+void main() {
+  bool tapped;
+  Widget tapTarget;
+
+  setUp(() {
+    tapped = false;
+    tapTarget = new GestureDetector(
+      onTap: () {
+        tapped = true;
+      },
+      child: new SizedBox(
+        width: 10.0,
+        height: 10.0,
+        child: new Text('target')
+      )
+    );
+  });
+
+  test('ModalBarrier prevents interactions with widgets behind it', () {
+    testWidgets((WidgetTester tester) {
+      Widget subject = new Stack(
+        children: <Widget>[
+          tapTarget,
+          new ModalBarrier(dismissable: false),
+        ]
+      );
+
+      tester.pumpWidget(subject);
+      tester.tap(tester.findText('target'));
+      tester.pumpWidget(subject);
+      expect(tapped, isFalse,
+        reason: 'because the tap is prevented by ModalBarrier');
+    });
+  });
+
+  test('ModalBarrier does not prevent interactions with widgets in front of it', () {
+    testWidgets((WidgetTester tester) {
+      Widget subject = new Stack(
+        children: <Widget>[
+          new ModalBarrier(dismissable: false),
+          tapTarget,
+        ]
+      );
+
+      tester.pumpWidget(subject);
+      tester.tap(tester.findText('target'));
+      tester.pumpWidget(subject);
+      expect(tapped, isTrue,
+        reason: 'because the tap is not prevented by ModalBarrier');
+    });
+  });
+
+  test('ModalBarrier pops the Navigator when dismissed', () {
+    testWidgets((WidgetTester tester) {
+      final Map<String, RouteBuilder> routes = <String, RouteBuilder>{
+        '/': (RouteArguments args) => new FirstComponent(),
+        '/modal': (RouteArguments args) => new SecondComponent(),
+      };
+
+      tester.pumpWidget(new MaterialApp(routes: routes));
+
+      // Initially the barrier is not visible
+      expect(tester.findElementByKey(const ValueKey('barrier')), isNull);
+
+      // Tapping on X routes to the barrier
+      tester.tap(tester.findText('X'));
+      tester.pump();  // begin transition
+      tester.pump(const Duration(seconds: 1));  // end transition
+
+      // Tap on the barrier to dismiss it
+      tester.tap(tester.findElementByKey(const ValueKey('barrier')));
+      tester.pump();  // begin transition
+      tester.pump(const Duration(seconds: 1));  // end transition
+
+      expect(tester.findElementByKey(const ValueKey('barrier')), isNull,
+        reason: 'because the barrier was dismissed');
+    });
+  });
+}
+
+class FirstComponent extends StatelessComponent {
+  Widget build(BuildContext context) {
+    return new GestureDetector(
+      onTap: () {
+        Navigator.pushNamed(context, '/modal');
+      },
+      child: new Container(
+        child: new Text('X')
+      )
+    );
+  }
+}
+
+class SecondComponent extends StatelessComponent {
+  Widget build(BuildContext context) {
+    return new ModalBarrier(
+      key: const ValueKey('barrier'),
+      dismissable: true
+    );
+  }
+}