Added missing tests for Table api example table.0.dart. (#147318)

Added missing tests for Table example. Issue #130459

dev/bots/check_code_samples.dart

@@ -410,7 +410,6 @@ final Set<String> _knownMissingTests = <String>{
   'examples/api/test/widgets/async/future_builder.0_test.dart',
   'examples/api/test/widgets/restoration_properties/restorable_value.0_test.dart',
   'examples/api/test/widgets/animated_size/animated_size.0_test.dart',
-  'examples/api/test/widgets/table/table.0_test.dart',
   'examples/api/test/widgets/animated_switcher/animated_switcher.0_test.dart',
   'examples/api/test/widgets/transitions/relative_positioned_transition.0_test.dart',
   'examples/api/test/widgets/transitions/positioned_transition.0_test.dart',

examples/api/test/widgets/table/table.0_test.dart

@@ -0,0 +1,39 @@
+// 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/widgets/table/table.0.dart' as example;
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  testWidgets('Table has expected arrangement', (WidgetTester tester) async {
+    await tester.pumpWidget(const example.TableExampleApp());
+
+    final Table table = tester.widget<Table>(find.byType(Table));
+
+    // Check the defined columnWidths.
+    expect(table.columnWidths, const <int, TableColumnWidth>{
+      0: IntrinsicColumnWidth(),
+      1: FlexColumnWidth(),
+      2: FixedColumnWidth(64),
+    });
+
+    // The table has two rows.
+    expect(table.children.length, 2);
+
+    for (int i = 0; i < table.children.length; i++) {
+      // Each row has three containers.
+      expect(table.children[i].children.length, 3);
+
+      // Returns the width of given widget.
+      double getWidgetWidth(Widget widget) {
+        return tester.getSize(find.byWidget(widget)).width;
+      }
+
+      // Check table row container width.
+      expect(getWidgetWidth(table.children[i].children.first), equals(128));
+      expect(getWidgetWidth(table.children[i].children[2]), equals(64));
+    }
+  });
+}