def test_breadth_first_bst():
bst = BinarySearchTree()
bst.add(4)
bst.add(9)
bst.add(-1)
bst.add(6)
bst.add(3)
bst.add(8)
bst.add(5)
actual = bst.breadth_first(bst)
expected = [4, 9, 6, 8, 5, -1, 3]
assert actual == expected
def test_breadth_3():
tree=BinarySearchTree()
assert tree.breadth_first() == 'Empty Tree'