def test_add_edge():
graph = Graph()
vertex_1 = graph.add_vertex('test1')
vertex_2 = graph.add_vertex('test2')
assert len(graph.get_neighbors(vertex_1)) == 0
graph.add_edge(vertex_1, vertex_2)
assert len(graph.get_neighbors(vertex_1)) == 1
def test_get_neighbors_none():
g = Graph()
node_a = g.add_node('a')
node_b = g.add_node('b')
node_c = g.add_node('c')
node_d = g.add_node('d')
actual = g.get_neighbors(node_a)
expected = []
assert actual == expected
def test_get_neighbors_1():
g = Graph()
node_a = g.add_node('a')
node_b = g.add_node('b')
node_c = g.add_node('c')
node_d = g.add_node('d')
g.add_edge(node_a, node_b)
actual = len(g.get_neighbors(node_a))
expected = 1
assert actual == expected
def test_get_neighbors():
graph = Graph()
test1 = graph.add_vertex('test1')
test2 = graph.add_vertex('test2')
graph.add_edge(test1, test2)
neighbors = graph.get_neighbors(test1)
assert len(neighbors) == 1
neighbor = neighbors[0]
assert neighbor.vertex.value == 'test2'
assert neighbor.weight == 1
def test_empty_graph():
graph = Graph()
assert graph.get_vertices() == None
assert graph.get_neighbors("key") == None
assert len(graph) == 0