def test_cursor_usage_to_add_a_chain():
a, b, c = get_pseudo_nodes(*"abc")
g = Graph()
g.get_cursor() >> a >> b >> c
assert len(g) == 3
assert g.outputs_of(BEGIN) == {g.index_of(a)}
assert g.outputs_of(a) == {g.index_of(b)}
assert g.outputs_of(b) == {g.index_of(c)}
assert g.outputs_of(c) == set()
def test_cursor_to_fork_a_graph():
a, b, c, d, e = get_pseudo_nodes(*"abcde")
g = Graph()
g >> a >> b >> c
g.get_cursor(b) >> d >> e
assert len(g) == 5
assert g.outputs_of(BEGIN) == {g.index_of(a)}
assert g.outputs_of(a) == {g.index_of(b)}
assert g.outputs_of(b) == {g.index_of(c), g.index_of(d)}
assert g.outputs_of(c) == set()
assert g.outputs_of(d) == {g.index_of(e)}
assert g.outputs_of(e) == set()
def test_get_cursor():
g = Graph()
cursor = g.get_cursor()
assert cursor.graph is g
assert cursor.first is BEGIN
assert cursor.last is BEGIN
def test_get_cursor_in_a_vacuum():
g = Graph()
cursor = g.get_cursor(None)
assert cursor.graph is g
assert cursor.first is None
assert cursor.last is None