new_contents: """Tests for vectors."""
  
  from sympy import sympify
  
  from drudge import Vec
  
  
  def test_vecs_has_basic_properties():
      """Tests the basic properties of vector instances."""
  
      base = Vec('v')
      v_ab = Vec('v', indices=['a', 'b'])
      v_ab_1 = base['a', 'b']
      v_ab_2 = (base['a'])['b']
  
      indices_ref = (sympify('a'), sympify('b'))
      hash_ref = hash(v_ab)
      str_ref = 'v[a, b]'
      repr_ref = "Vec('v', (a, b))"
  
      for i in [v_ab, v_ab_1, v_ab_2]:
          assert i.base == base.base
          assert i.indices == indices_ref
          assert hash(i) == hash_ref
          assert i == v_ab
          assert str(i) == str_ref
          assert repr(i) == repr_ref
  
subject: Add tests for vectors