'Tests that a graph with isolated nodes has all isolates in
one block of the partition.'

def test_isolates(self):

    G = nx.empty_graph(5)
    cells = nx.voronoi_cells(G, {0, 2, 4})
    expected = {0: {0}, 2: {2}, 4: {4}, 'unreachable': {1, 3}}
    assert_equal(expected, cells)
