def test_length(self):
"""make sure we can test length"""
x = PySparseMatInt(3,4)
self.assertEqual(x.length(), 0)
x.insert(1,2,10)
self.assertEqual(x.length(), 1)
x.insert(2,3,4)
x.insert(2,3,4)
x.insert(2,3,4)
self.assertEqual(x.length(), 2)
x.erase(2,3)
self.assertEqual(x.length(), 1)
