def test_quantum_harmonic_oscillator(self):
     grids = np.linspace(-5, 5, 501)
     dx = single_electron.get_dx(grids)
     # Exact ground state density of the quantum harmonic oscillator (k=1):
     # \pi^(-1/2) \exp(-x^2)
     density = np.sqrt(1 / np.pi) * np.exp(-grids**2)
     # Its corresponding kinetic energy is 0.25.
     np.testing.assert_allclose(single_electron.vw_grid(density, dx),
                                0.25,
                                atol=1e-7)
 def test_get_dx(self):
     np.testing.assert_allclose(
         single_electron.get_dx(np.linspace(0, 1, 11)), 0.1)