public function test_that_it_allows_color_replacement()
{
$monday = WeekDay::MONDAY();
$node = new RedBlackNode($monday, 'Monday', 1, RedBlackNode::RED);
$node->setColor(RedBlackNode::BLACK);
$this->assertSame(RedBlackNode::BLACK, $node->color());
}
/**
* Flips the colors of a node and its two children
*
* Used to maintain symmetric order and perfect black balance when a black
* node has two red children.
*
* @param RedBlackNode $node The node
*
* @return void
*/
protected function flipColors(RedBlackNode $node)
{
$node->setColor(!$node->color());
$node->left()->setColor(!$node->left()->color());
$node->right()->setColor(!$node->right()->color());
}