old_contents: from geonet.network import Net
  
  def test_Net():
      nodes = ['a', 'b', 'c']
      arcs = [('a', 'b'), ('b', 'c'), ('a', 'c')]
  
      net = Net(nodes, arcs)
      assert set(net.get_nodes()) == set(nodes)
      assert set(net.get_arcs()) == set(arcs)
  
new_contents: from geonet.network import Net, SteinerTree
  
  def test_Net():
      nodes = ['a', 'b', 'c']
      arcs = [('a', 'b'), ('b', 'c'), ('a', 'c')]
  
      net = Net(nodes, arcs)
      assert set(net.get_nodes()) == set(nodes)
      assert set(net.get_arcs()) == set(arcs)
  
  def test_SteinerTree():
      nodes = ['a', 'b', 'c', 's']
      arcs = [('a', 's'), ('b', 's'), ('c', 's')]
      pos = {'a': (0,0), 'b': (1,0), 'c': (0,1)}
  
      tree = SteinerTree(nodes, arcs, pos)
  
      for n in 'abc':
          assert tree.is_terminal(n)
      assert tree.is_steiner('s')
  
subject: add more tests for network