Write unit tests for API Examples of checkbox.0, checkbox.1 (#144888)

Write unit tests for API Examples of checkbox.0, checkbox.1

Part of  #130459

dev/bots/check_code_samples.dart

@@ -371,8 +371,6 @@ final Set<String> _knownMissingTests = <String>{
   'examples/api/test/material/app_bar/sliver_app_bar.3_test.dart',
   'examples/api/test/material/banner/material_banner.1_test.dart',
   'examples/api/test/material/banner/material_banner.0_test.dart',
-  'examples/api/test/material/checkbox/checkbox.1_test.dart',
-  'examples/api/test/material/checkbox/checkbox.0_test.dart',
   'examples/api/test/material/navigation_rail/navigation_rail.extended_animation.0_test.dart',
   'examples/api/test/rendering/growth_direction/growth_direction.0_test.dart',
   'examples/api/test/rendering/sliver_grid/sliver_grid_delegate_with_fixed_cross_axis_count.0_test.dart',

examples/api/test/material/checkbox/checkbox.0_test.dart

@@ -0,0 +1,59 @@
+// 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/material.dart';
+import 'package:flutter_api_samples/material/checkbox/checkbox.0.dart'
+    as example;
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  testWidgets('Checkbox can be checked', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      const example.CheckboxExampleApp(),
+    );
+
+    Checkbox checkbox = tester.widget(find.byType(Checkbox));
+    expect(checkbox.value, isFalse);
+
+    await tester.tap(find.byType(Checkbox));
+    await tester.pump();
+
+    checkbox = tester.widget(find.byType(Checkbox));
+    expect(checkbox.value, isTrue);
+
+    await tester.tap(find.byType(Checkbox));
+    await tester.pump();
+
+    checkbox = tester.widget(find.byType(Checkbox));
+    expect(checkbox.value, isFalse);
+  });
+
+  testWidgets('Checkbox color can be changed', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      const example.CheckboxExampleApp(),
+    );
+    final Checkbox checkbox = tester.widget(find.byType(Checkbox));
+
+    expect(
+      checkbox.checkColor,
+      Colors.white,
+    );
+    expect(
+      checkbox.fillColor!.resolve(<MaterialState>{}),
+      Colors.red,
+    );
+    expect(
+      checkbox.fillColor!.resolve(<MaterialState>{MaterialState.pressed}),
+      Colors.blue,
+    );
+    expect(
+      checkbox.fillColor!.resolve(<MaterialState>{MaterialState.hovered}),
+      Colors.blue,
+    );
+    expect(
+      checkbox.fillColor!.resolve(<MaterialState>{MaterialState.focused}),
+      Colors.blue,
+    );
+  });
+}

examples/api/test/material/checkbox/checkbox.1_test.dart

@@ -0,0 +1,68 @@
+// 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/material.dart';
+import 'package:flutter_api_samples/material/checkbox/checkbox.1.dart'
+    as example;
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  testWidgets('Checkbox can be checked', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      const example.CheckboxExampleApp(),
+    );
+
+    expect(find.byType(Checkbox), findsNWidgets(3));
+    Checkbox checkbox = tester.widget(find.byType(Checkbox).first);
+    Checkbox checkboxWithError = tester.widget(find.byType(Checkbox).at(1));
+    Checkbox checkboxDisabled = tester.widget(find.byType(Checkbox).last);
+
+    // Verify the initial state of the checkboxes.
+    expect(checkbox.value, isTrue);
+    expect(checkboxWithError.value, isTrue);
+    expect(checkboxDisabled.value, isTrue);
+
+    expect(checkboxWithError.isError, isTrue);
+    expect(checkboxDisabled.onChanged, null);
+
+    expect(checkbox.tristate, isTrue);
+    expect(checkboxWithError.tristate, isTrue);
+    expect(checkboxDisabled.tristate, isTrue);
+
+    // Tap the first Checkbox and verify the state change.
+    await tester.tap(find.byType(Checkbox).first);
+    await tester.pump();
+    checkbox = tester.widget(find.byType(Checkbox).first);
+    checkboxWithError = tester.widget(find.byType(Checkbox).at(1));
+    checkboxDisabled = tester.widget(find.byType(Checkbox).last);
+
+    expect(checkbox.value, isNull);
+    expect(checkboxWithError.value, isNull);
+    expect(checkboxDisabled.value, isNull);
+
+    // Tap the second Checkbox and verify the state change.
+    await tester.tap(find.byType(Checkbox).at(1));
+    await tester.pump();
+
+    checkbox = tester.widget(find.byType(Checkbox).first);
+    checkboxWithError = tester.widget(find.byType(Checkbox).at(1));
+    checkboxDisabled = tester.widget(find.byType(Checkbox).last);
+
+    expect(checkbox.value, isFalse);
+    expect(checkboxWithError.value, isFalse);
+    expect(checkboxDisabled.value, isFalse);
+
+    // Tap the third Checkbox and verify that should remain unchanged.
+    await tester.tap(find.byType(Checkbox).last);
+    await tester.pump();
+
+    checkbox = tester.widget(find.byType(Checkbox).first);
+    checkboxWithError = tester.widget(find.byType(Checkbox).at(1));
+    checkboxDisabled = tester.widget(find.byType(Checkbox).last);
+
+    expect(checkbox.value, isFalse);
+    expect(checkboxWithError.value, isFalse);
+    expect(checkboxDisabled.value, isFalse);
+  });
+}