def test_add(self):
"""
Test creating node trees.
"""
tree = Tree()
n1 = 'n1'
n2 = 'n2'
n3 = 'n3'
tree.add(n1)
assert len(tree._nodes) == 1
assert len(tree._children) == 2
assert len(tree._children[None]) == 1
assert len(tree._children[n1]) == 0
tree.add(n2)
tree.add(n3, parent=n1)
assert len(tree._nodes) == 3
assert len(tree._children) == 4
assert len(tree._children[None]) == 2
assert len(tree._children[n1]) == 1
assert len(tree._children[n2]) == 0
assert len(tree._children[n2]) == 0
assert tree._nodes == [n1, n3, n2]
n4 = 'n4'
tree.add(n4, parent=n3)
assert tree._nodes == [n1, n3, n4, n2]
n5 = 'n5'
tree.add(n5, parent=n3)
assert tree._nodes == [n1, n3, n4, n5, n2]
n6 = 'n6'
tree.add(n6, parent=n2)
assert tree._nodes == [n1, n3, n4, n5, n2, n6]
n7 = 'n7'
tree.add(n7, parent=n1)
assert len(tree._children) == 8
assert tree._nodes == [n1, n3, n4, n5, n7, n2, n6]
assert tree.get_parent(n7) is n1
assert tree.get_parent(n6) is n2
assert tree.get_parent(n5) is n3
assert tree.get_parent(n4) is n3
assert tree.get_parent(n3) is n1
assert tree.get_parent(n2) is None
assert tree.get_parent(n1) is None
