test.m

- (ASLayoutSpec *)layoutSpecThatFits:(ASSizeRange)constrainedSize {
    _node1.style.preferredSize = CGSizeMake(constrainedSize.max.width, 200);
    _node2.style.preferredSize = CGSizeMake(constrainedSize.max.width, 40);

    _node3.style.height = _currentState == StateTypeSmall ? ASDimensionMakeWithPoints(300) : ASDimensionMakeWithPoints(450);

	ASDisplayNode *spacer = [][ASDisplayNode alloc] init];
	spacer.style.flexGrow = 1.0;

    return [ASStackLayoutSpec stackLayoutSpecWithDirection:ASStackLayoutDirectionVertical
                                                   spacing:0
                                            justifyContent:ASStackLayoutJustifyContentStart
                                                alignItems:ASStackLayoutAlignItemsStretch
                                                  children:@[
												  	_node1,
													_node2,
													_spacer,
													_node3
												  ]];
}

- (void) testButton {
	_currentState = _currentState == StateTypeSmall ? StateTypeLarge : StateTypeSmall;
	[self setNeedsLayout];
}