new_contents: import unittest2
  
  from penchy.jobs.dependency import Edge, edgesort
  
  
  class EdgeSortTest(unittest2.TestCase):
  
      def test_circ(self):
          edges = [Edge(1, 2), Edge(2, 1)]
          with self.assertRaises(ValueError):
              edgesort(edges)
  
      def test_linear(self):
          edges = [Edge(0, 1), Edge(1, 2)]
          self.assertListEqual(edgesort(edges), range(3))
  
      def test_multi_deps(self):
          edges = [Edge(0, 1), Edge(2, 1),
                   Edge(0, 2)]
          self.assertListEqual(edgesort(edges), [0,2,1])
subject: Add tests for edgesort.