old_contents: from csympy import Symbol, Integer, sympify, SympifyError
  import sympy
  
  def test_conv1():
      x = Symbol("x")
      assert x._sympy_() == sympy.Symbol("x")
      assert x._sympy_() != sympy.Symbol("y")
      x = Symbol("y")
      assert x._sympy_() != sympy.Symbol("x")
      assert x._sympy_() == sympy.Symbol("y")
  
  def test_conv2():
      x = Symbol("x")
      y = Symbol("y")
      z = Symbol("z")
      e = x*y
      assert e._sympy_() == sympy.Symbol("x")*sympy.Symbol("y")
      e = x*y*z
      assert e._sympy_() == sympy.Symbol("x")*sympy.Symbol("y")*sympy.Symbol("z")
  
  def test_conv3():
      x = Symbol("x")
      y = Symbol("y")
      z = Symbol("z")
      e = x+y
      assert e._sympy_() == sympy.Symbol("x")+sympy.Symbol("y")
      e = x+y+z
      assert e._sympy_() == sympy.Symbol("x")+sympy.Symbol("y")+sympy.Symbol("z")
  
  def test_conv4():
      x = Symbol("x")
      y = Symbol("y")
      z = Symbol("z")
      e = x**y
      assert e._sympy_() == sympy.Symbol("x")**sympy.Symbol("y")
      e = (x+y)**z
      assert sympy.sympify(e) == (sympy.Symbol("x")+sympy.Symbol("y"))**sympy.Symbol("z")
  
  def test_conv5():
      x = Integer(5)
      y = Integer(6)
      assert sympy.sympify(x) == sympy.Integer(5)
      assert sympy.sympify(x/y) == sympy.Integer(5) / sympy.Integer(6)
  
  def test_conv6():
      x = Symbol("x")
      y = Symbol("y")
      assert (x/3)._sympy_() == sympy.Symbol("x") / 3
      assert (3*x)._sympy_() == 3*sympy.Symbol("x")
      assert sympy.sympify(3+x) == 3+sympy.Symbol("x")
      #assert sympy.sympify(3-x) == 3-sympy.Symbol("x")
      assert (x/y)._sympy_() == sympy.Symbol("x") / sympy.Symbol("y")
  
new_contents: from csympy import Symbol, Integer, sympify, SympifyError
  import sympy
  
  def test_conv1():
      x = Symbol("x")
      assert x._sympy_() == sympy.Symbol("x")
      assert x._sympy_() != sympy.Symbol("y")
      x = Symbol("y")
      assert x._sympy_() != sympy.Symbol("x")
      assert x._sympy_() == sympy.Symbol("y")
  
  def test_conv2():
      x = Symbol("x")
      y = Symbol("y")
      z = Symbol("z")
      e = x*y
      assert e._sympy_() == sympy.Symbol("x")*sympy.Symbol("y")
      e = x*y*z
      assert e._sympy_() == sympy.Symbol("x")*sympy.Symbol("y")*sympy.Symbol("z")
  
  def test_conv3():
      x = Symbol("x")
      y = Symbol("y")
      z = Symbol("z")
      e = x+y
      assert e._sympy_() == sympy.Symbol("x")+sympy.Symbol("y")
      e = x+y+z
      assert e._sympy_() == sympy.Symbol("x")+sympy.Symbol("y")+sympy.Symbol("z")
  
  def test_conv4():
      x = Symbol("x")
      y = Symbol("y")
      z = Symbol("z")
      e = x**y
      assert e._sympy_() == sympy.Symbol("x")**sympy.Symbol("y")
      e = (x+y)**z
      assert e._sympy_() == (sympy.Symbol("x")+sympy.Symbol("y"))**sympy.Symbol("z")
  
  def test_conv5():
      x = Integer(5)
      y = Integer(6)
      assert x._sympy_() == sympy.Integer(5)
      assert (x/y)._sympy_() == sympy.Integer(5) / sympy.Integer(6)
  
  def test_conv6():
      x = Symbol("x")
      y = Symbol("y")
      assert (x/3)._sympy_() == sympy.Symbol("x") / 3
      assert (3*x)._sympy_() == 3*sympy.Symbol("x")
      assert (3+x)._sympy_() == 3+sympy.Symbol("x")
      assert (3-x)._sympy_() == 3-sympy.Symbol("x")
      assert (x/y)._sympy_() == sympy.Symbol("x") / sympy.Symbol("y")
  
subject: Improve tests