old_contents: import pytest
  
  # This project
  from ..util import from_equation
  from .helpers import PotentialTestBase
  
  
  class EquationBase(PotentialTestBase):
      def test_plot(self):
          # Skip for now because contour plotting assumes 3D
          pass
  
      def test_pickle(self):
          # Skip for now because these are not picklable
          pass
  
      def test_save_load(self):
          # Skip for now because these can't be written to YAML
          pass
  
  
  class TestHarmonicOscillatorFromEquation(EquationBase):
      Potential = from_equation("1/2*k*x**2", vars="x", pars="k",
                                name='HarmonicOscillator',
                                hessian=True)
      potential = Potential(k=1.)
      w0 = [1., 0.]
  
      def test_derp(self):
          import numpy as np
          self.potential.gradient(np.random.random(size=(1,13)))
  
      @pytest.mark.skip(reason="to_sympy() not implemented")
      def test_against_sympy(self):
          pass
  
  
  # class TestHarmonicOscillatorFromEquationUnits(EquationBase):
  #     Potential = from_equation("1/2*k*x**2", vars="x", pars="k",
  #                               name='HarmonicOscillator',
  #                               hessian=True)
  #     potential = Potential(k=1., units=solarsystem)
  #     w0 = [1.,0.]
  
  # class TestKeplerFromEquation(EquationBase):
  #     Potential = from_equation("-G*M/sqrt(x**2+y**2+z**2)", vars=["x","y","z"],
  #                               pars=["G","M"], name='Kepler',
  #                               hessian=True)
  #     potential = Potential(G=1., M=1., units=solarsystem)
  #     w0 = [1.,0.,0.,0.,6.28,0.]
  
new_contents: import pytest
  
  # This project
  from ..util import from_equation
  from .helpers import PotentialTestBase
  
  try:
      import sympy # noqa
      HAS_SYMPY = True
  except ImportError:
      HAS_SYMPY = False
  
  
  class EquationBase(PotentialTestBase):
      def test_plot(self):
          # Skip for now because contour plotting assumes 3D
          pass
  
      def test_pickle(self):
          # Skip for now because these are not picklable
          pass
  
      def test_save_load(self):
          # Skip for now because these can't be written to YAML
          pass
  
  
  if HAS_SYMPY:
      class TestHarmonicOscillatorFromEquation(EquationBase):
          Potential = from_equation("1/2*k*x**2", vars="x", pars="k",
                                    name='HarmonicOscillator',
                                    hessian=True)
          potential = Potential(k=1.)
          w0 = [1., 0.]
  
          def test_derp(self):
              import numpy as np
              self.potential.gradient(np.random.random(size=(1,13)))
  
          @pytest.mark.skip(reason="to_sympy() not implemented")
          def test_against_sympy(self):
              pass
  
  
  # class TestHarmonicOscillatorFromEquationUnits(EquationBase):
  #     Potential = from_equation("1/2*k*x**2", vars="x", pars="k",
  #                               name='HarmonicOscillator',
  #                               hessian=True)
  #     potential = Potential(k=1., units=solarsystem)
  #     w0 = [1.,0.]
  
  # class TestKeplerFromEquation(EquationBase):
  #     Potential = from_equation("-G*M/sqrt(x**2+y**2+z**2)", vars=["x","y","z"],
  #                               pars=["G","M"], name='Kepler',
  #                               hessian=True)
  #     potential = Potential(G=1., M=1., units=solarsystem)
  #     w0 = [1.,0.,0.,0.,6.28,0.]
  
subject: fix test that requires sympy