def test_maximum_value():
new_tree = BinaryTree()
expected = 11
new_tree.add(2)
new_tree.add(7)
new_tree.add(5)
new_tree.add(2)
new_tree.add(6)
new_tree.add(9)
new_tree.add(5)
new_tree.add(11)
new_tree.add(4)
assert new_tree.find_maximum_value() == expected
def test_negative_max_value():
new_tree = BinaryTree()
expected = -2
new_tree.add(-2)
new_tree.add(-3)
new_tree.add(-7)
new_tree.add(-5)
new_tree.add(-2)
new_tree.add(-6)
new_tree.add(-9)
new_tree.add(-5)
new_tree.add(-11)
new_tree.add(-4)
assert new_tree.find_maximum_value() == expected