def test_center():
"""Test getting and setting the center."""
ellipse = Ellipse(1, 2)
assert all(ellipse.center == (0, 0, 0))
center = (1, 1, 1)
ellipse.center = center
assert all(ellipse.center == center)
def test_moment_inertia(a, b, center):
ellipse = Ellipse(a, b)
assert np.all(np.asarray(ellipse.planar_moments_inertia) >= 0)
# We must set the center after construction so that the inertia tensor
# calculation is not shifted away from the origin.
ellipse.center = center
area = ellipse.area
expected = [np.pi / 4 * a * b**3, np.pi / 4 * a**3 * b, 0]
expected[0] += area * center[0]**2
expected[1] += area * center[1]**2
expected[2] = area * center[0] * center[1]
np.testing.assert_allclose(ellipse.planar_moments_inertia[:2],
expected[:2])
np.testing.assert_allclose(ellipse.planar_moments_inertia[2], expected[2])
assert ellipse.polar_moment_inertia == pytest.approx(sum(expected[:2]))
def test_inertia_tensor():
"""Test the inertia tensor calculation."""
ellipse = Ellipse(1, 2)
ellipse.center = (0, 0, 0)
assert np.sum(ellipse.inertia_tensor > 1e-6) == 1
assert ellipse.inertia_tensor[2, 2] == 5 * np.pi / 2