def test_citnet_add_edge():
"""
Check if an edge is added correctly
"""
citnet = CitationNetwork()
edge = ('1975NW.....62..309F', '1963RvMP...35..947B', 0)
citnet.add_edge(edge)
assert citnet.has_edge(edge)
def test_citnet_add_edge_two_times():
"""
Make sure that no duplicates can be added
"""
citnet = CitationNetwork()
edge = ('1975NW.....62..309F', '1963RvMP...35..947B', 0)
citnet.add_edge(edge)
citnet.add_edge(edge)
assert len(citnet.edges) == 1