text: import pytest
  import networkx as nx
  from networkx import NetworkXNotImplemented
  
  
  class TestAttractingComponents:
      @classmethod
      def setup_class(cls):
          cls.G1 = nx.DiGraph()
          cls.G1.add_edges_from(
              [
                  (5, 11),
                  (11, 2),
                  (11, 9),
                  (11, 10),
                  (7, 11),
                  (7, 8),
                  (8, 9),
                  (3, 8),
                  (3, 10),
              ]
          )
          cls.G2 = nx.DiGraph()
          cls.G2.add_edges_from([(0, 1), (0, 2), (1, 1), (1, 2), (2, 1)])
  
          cls.G3 = nx.DiGraph()
          cls.G3.add_edges_from([(0, 1), (1, 2), (2, 1), (0, 3), (3, 4), (4, 3)])
  
          cls.G4 = nx.DiGraph()
  
      def test_attracting_components(self):
          ac = list(nx.attracting_components(self.G1))
          assert {2} in ac
          assert {9} in ac
          assert {10} in ac
  
          ac = list(nx.attracting_components(self.G2))
          ac = [tuple(sorted(x)) for x in ac]
          assert ac == [(1, 2)]
  
          ac = list(nx.attracting_components(self.G3))
          ac = [tuple(sorted(x)) for x in ac]
          assert (1, 2) in ac
          assert (3, 4) in ac
          assert len(ac) == 2
  
          ac = list(nx.attracting_components(self.G4))
          assert ac == []
  
      def test_number_attacting_components(self):
          assert nx.number_attracting_components(self.G1) == 3
          assert nx.number_attracting_components(self.G2) == 1
          assert nx.number_attracting_components(self.G3) == 2
          assert nx.number_attracting_components(self.G4) == 0
  
      def test_is_attracting_component(self):
          assert not nx.is_attracting_component(self.G1)
          assert not nx.is_attracting_component(self.G2)
          assert not nx.is_attracting_component(self.G3)
          g2 = self.G3.subgraph([1, 2])
          assert nx.is_attracting_component(g2)
          assert not nx.is_attracting_component(self.G4)
  
      def test_connected_raise(self):
          G = nx.Graph()
          with pytest.raises(NetworkXNotImplemented):
              next(nx.attracting_components(G))
          pytest.raises(NetworkXNotImplemented, nx.number_attracting_components, G)
          pytest.raises(NetworkXNotImplemented, nx.is_attracting_component, G)
  