"""Unit tests for the :mod:`networkx.generators.mycielski` module."""

import pytest

import networkx as nx


class TestMycielski:
    def test_construction(self):
        G = nx.path_graph(2)
        M = nx.mycielskian(G)
        assert nx.is_isomorphic(M, nx.cycle_graph(5))

    def test_size(self):
        G = nx.path_graph(2)
        M = nx.mycielskian(G, 2)
        assert len(M) == 11
        assert M.size() == 20

    def test_mycielski_graph_generator(self):
        G = nx.mycielski_graph(1)
        assert nx.is_isomorphic(G, nx.empty_graph(1))
        G = nx.mycielski_graph(2)
        assert nx.is_isomorphic(G, nx.path_graph(2))
        G = nx.mycielski_graph(3)
        assert nx.is_isomorphic(G, nx.cycle_graph(5))
        G = nx.mycielski_graph(4)
        assert nx.is_isomorphic(G, nx.mycielskian(nx.cycle_graph(5)))
        with pytest.raises(nx.NetworkXError, match="must satisfy n >= 1"):
            nx.mycielski_graph(0)