@Test(dataProvider = "treeLevels")
public void crossover1(final int level1, final int level2) {

	final Random random = new Random();
	final TreeNode<Integer> tree1 = newTree(level1, random);
	final TreeNode<Integer> tree2 = newTree(level2, random);
	final int size1 = tree1.size();
	final int size2 = tree2.size();
	SingleNodeCrossover.swap(tree1, tree2);
	Assert.assertEquals(tree1.size() + tree2.size(), size1 + size2);
}