custom_one_child_layout_test.dart

// Copyright 2015 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/rendering.dart';
import 'package:flutter/widgets.dart';

class TestSingleChildLayoutDelegate extends SingleChildLayoutDelegate {
  BoxConstraints constraintsFromGetSize;
  BoxConstraints constraintsFromGetConstraintsForChild;
  Size sizeFromGetPositionForChild;
  Size childSizeFromGetPositionForChild;

  @override
  Size getSize(BoxConstraints constraints) {
    if (!RenderObject.debugCheckingIntrinsics)
      constraintsFromGetSize = constraints;
    return new Size(200.0, 300.0);
  }

  @override
  BoxConstraints getConstraintsForChild(BoxConstraints constraints) {
    assert(!RenderObject.debugCheckingIntrinsics);
    constraintsFromGetConstraintsForChild = constraints;
    return new BoxConstraints(
      minWidth: 100.0,
      maxWidth: 150.0,
      minHeight: 200.0,
      maxHeight: 400.0
    );
  }

  @override
  Offset getPositionForChild(Size size, Size childSize) {
    assert(!RenderObject.debugCheckingIntrinsics);
    sizeFromGetPositionForChild = size;
    childSizeFromGetPositionForChild = childSize;
    return Offset.zero;
  }

  bool shouldRelayoutCalled = false;
  bool shouldRelayoutValue = false;

  @override
  bool shouldRelayout(_) {
    assert(!RenderObject.debugCheckingIntrinsics);
    shouldRelayoutCalled = true;
    return shouldRelayoutValue;
  }
}

Widget buildFrame(SingleChildLayoutDelegate delegate) {
  return new Center(child: new CustomSingleChildLayout(delegate: delegate, child: new Container()));
}

void main() {
  testWidgets('Control test for CustomSingleChildLayout', (WidgetTester tester) async {
      TestSingleChildLayoutDelegate delegate = new TestSingleChildLayoutDelegate();
      await tester.pumpWidget(buildFrame(delegate));

      expect(delegate.constraintsFromGetSize.minWidth, 0.0);
      expect(delegate.constraintsFromGetSize.maxWidth, 800.0);
      expect(delegate.constraintsFromGetSize.minHeight, 0.0);
      expect(delegate.constraintsFromGetSize.maxHeight, 600.0);

      expect(delegate.constraintsFromGetConstraintsForChild.minWidth, 0.0);
      expect(delegate.constraintsFromGetConstraintsForChild.maxWidth, 800.0);
      expect(delegate.constraintsFromGetConstraintsForChild.minHeight, 0.0);
      expect(delegate.constraintsFromGetConstraintsForChild.maxHeight, 600.0);

      expect(delegate.sizeFromGetPositionForChild.width, 200.0);
      expect(delegate.sizeFromGetPositionForChild.height, 300.0);

      expect(delegate.childSizeFromGetPositionForChild.width, 150.0);
      expect(delegate.childSizeFromGetPositionForChild.height, 400.0);
  });

  testWidgets('Test SingleChildDelegate shouldRelayout method', (WidgetTester tester) async {
      TestSingleChildLayoutDelegate delegate = new TestSingleChildLayoutDelegate();
      await tester.pumpWidget(buildFrame(delegate));

      // Layout happened because the delegate was set.
      expect(delegate.constraintsFromGetConstraintsForChild, isNotNull); // i.e. layout happened
      expect(delegate.shouldRelayoutCalled, isFalse);

      // Layout did not happen because shouldRelayout() returned false.
      delegate = new TestSingleChildLayoutDelegate();
      delegate.shouldRelayoutValue = false;
      await tester.pumpWidget(buildFrame(delegate));
      expect(delegate.shouldRelayoutCalled, isTrue);
      expect(delegate.constraintsFromGetConstraintsForChild, isNull);

      // Layout happened because shouldRelayout() returned true.
      delegate = new TestSingleChildLayoutDelegate();
      delegate.shouldRelayoutValue = true;
      await tester.pumpWidget(buildFrame(delegate));
      expect(delegate.shouldRelayoutCalled, isTrue);
      expect(delegate.constraintsFromGetConstraintsForChild, isNotNull);
  });

}