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import networkx as nx
import networkx.algorithms.approximation as apxa
def test_ramsey():
# this should only find the complete graph
graph = nx.complete_graph(10)
c, i = apxa.ramsey_R2(graph)
cdens = nx.density(graph.subgraph(c))
assert cdens == 1.0, "clique not correctly found by ramsey!"
idens = nx.density(graph.subgraph(i))
assert idens == 0.0, "i-set not correctly found by ramsey!"
# this trivial graph has no cliques. should just find i-sets
graph = nx.trivial_graph()
c, i = apxa.ramsey_R2(graph)
assert c == {0}, "clique not correctly found by ramsey!"
assert i == {0}, "i-set not correctly found by ramsey!"
graph = nx.barbell_graph(10, 5, nx.Graph())
c, i = apxa.ramsey_R2(graph)
cdens = nx.density(graph.subgraph(c))
assert cdens == 1.0, "clique not correctly found by ramsey!"
idens = nx.density(graph.subgraph(i))
assert idens == 0.0, "i-set not correctly found by ramsey!"
# add self-loops and test again
graph.add_edges_from([(n, n) for n in range(0, len(graph), 2)])
cc, ii = apxa.ramsey_R2(graph)
assert cc == c
assert ii == i
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