def test_djikstra():
'''
Test `djikstra` function.
This is an implementation of Djikstra's algorithm
for finding shortest path distances to all nodes
in a graph from a specified start node.
'''
G = make_graph('test_data/undirected.txt')
expected = {'A': 0, 'C': 3, 'B': 1, 'D': 4}
dist = djikstra(G, 'A')
assert dist == expected
G = make_graph('test_data/directed.txt')
dist = djikstra(G, 'A')
assert dist == expected
def test_make_graph():
'''
Test `make_graph` function.
'''
G = make_graph('test_data/undirected.txt')
assert G['A']['B'] == 1
assert G['B']['A'] == 1
assert G['A']['C'] == 5
assert G['C']['A'] == 5
assert_raises(KeyError, G['A'].__getitem__, 'D')
assert_raises(KeyError, G['D'].__getitem__, 'A')
G = make_graph('test_data/directed.txt')
assert G['B']['A'] == 1
assert G['C']['A'] == 5
assert G['C']['B'] == 2
assert_raises(KeyError, G['A'].__getitem__, 'B')