packages/flutter/test/semantics/semantics_binding_test.dart

// Copyright 2014 The Flutter 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/semantics.dart';
import 'package:flutter_test/flutter_test.dart';

void main() {
  testWidgets('Listeners are called when semantics are turned on with ensureSemantics', (WidgetTester tester) async {
    expect(SemanticsBinding.instance.semanticsEnabled, isFalse);

    final List<bool> status = <bool>[];
    void listener() {
      status.add(SemanticsBinding.instance.semanticsEnabled);
    }

    SemanticsBinding.instance.addSemanticsEnabledListener(listener);
    expect(SemanticsBinding.instance.semanticsEnabled, isFalse);

    final SemanticsHandle handle1 = SemanticsBinding.instance.ensureSemantics();
    expect(status.single, isTrue);
    expect(SemanticsBinding.instance.semanticsEnabled, isTrue);
    status.clear();

    final SemanticsHandle handle2 = SemanticsBinding.instance.ensureSemantics();
    expect(status, isEmpty); // Listener didn't fire again.
    expect(SemanticsBinding.instance.semanticsEnabled, isTrue);

    expect(tester.binding.platformDispatcher.semanticsEnabled, isFalse);
    tester.binding.platformDispatcher.semanticsEnabledTestValue = true;
    expect(tester.binding.platformDispatcher.semanticsEnabled, isTrue);
    tester.binding.platformDispatcher.clearSemanticsEnabledTestValue();
    expect(tester.binding.platformDispatcher.semanticsEnabled, isFalse);
    expect(status, isEmpty); // Listener didn't fire again.
    expect(SemanticsBinding.instance.semanticsEnabled, isTrue);

    handle1.dispose();
    expect(status, isEmpty); // Listener didn't fire.
    expect(SemanticsBinding.instance.semanticsEnabled, isTrue);

    handle2.dispose();
    expect(status.single, isFalse);
    expect(SemanticsBinding.instance.semanticsEnabled, isFalse);
  }, semanticsEnabled: false);

  testWidgets('Listeners are called when semantics are turned on by platform', (WidgetTester tester) async {
    expect(SemanticsBinding.instance.semanticsEnabled, isFalse);

    final List<bool> status = <bool>[];
    void listener() {
      status.add(SemanticsBinding.instance.semanticsEnabled);
    }

    SemanticsBinding.instance.addSemanticsEnabledListener(listener);
    expect(SemanticsBinding.instance.semanticsEnabled, isFalse);

    tester.binding.platformDispatcher.semanticsEnabledTestValue = true;
    expect(status.single, isTrue);
    expect(SemanticsBinding.instance.semanticsEnabled, isTrue);
    status.clear();

    final SemanticsHandle handle = SemanticsBinding.instance.ensureSemantics();
    handle.dispose();
    expect(status, isEmpty); // Listener didn't fire.
    expect(SemanticsBinding.instance.semanticsEnabled, isTrue);

    tester.binding.platformDispatcher.clearSemanticsEnabledTestValue();
    expect(status.single, isFalse);
    expect(SemanticsBinding.instance.semanticsEnabled, isFalse);
  }, semanticsEnabled: false);

  testWidgets('SemanticsBinding.ensureSemantics triggers creation of semantics owner.', (WidgetTester tester) async {
    expect(SemanticsBinding.instance.semanticsEnabled, isFalse);
    expect(tester.binding.pipelineOwner.semanticsOwner, isNull);

    final SemanticsHandle handle = SemanticsBinding.instance.ensureSemantics();
    expect(SemanticsBinding.instance.semanticsEnabled, isTrue);
    expect(tester.binding.pipelineOwner.semanticsOwner, isNotNull);

    handle.dispose();
    expect(SemanticsBinding.instance.semanticsEnabled, isFalse);
    expect(tester.binding.pipelineOwner.semanticsOwner, isNull);
  }, semanticsEnabled: false);
}