def test_invalid_a_b_constructor(a, b):
"""Test invalid a, b values in constructor."""
with pytest.raises(ValueError):
Ellipse(a, b)
with pytest.raises(ValueError):
Ellipse(b, a)
with pytest.raises(ValueError):
Ellipse(a, a)
def test_invalid_a_b_setter(a):
"""Test setting invalid a, b values."""
ellipse = Ellipse(1, 1)
with pytest.raises(ValueError):
ellipse.a = a
with pytest.raises(ValueError):
ellipse.b = a
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_a_b_getter_setter(a, b):
"""Test getter and setter for a and b."""
ellipse = Ellipse(a, b)
assert ellipse.a == a
assert ellipse.b == b
ellipse.a = a + 1
ellipse.b = b + 1
assert ellipse.a == a + 1
assert ellipse.b == b + 1
def test_perimeter(a, b):
"""Check surface area against an approximate formula."""
# Uses Ramanujan's approximation for the circumference of an ellipse:
# https://en.wikipedia.org/wiki/Ellipse#Circumference
ellipse = Ellipse(a, b)
b, a = sorted([a, b])
h = (a - b)**2 / (a + b)**2
approx_perimeter = np.pi * (a + b) * (1 + 3 * h /
(10 + np.sqrt(4 - 3 * h)))
assert ellipse.perimeter == pytest.approx(approx_perimeter, rel=1e-3)
assert ellipse.circumference == pytest.approx(approx_perimeter, rel=1e-3)
def test_set_area(a, b, area):
"""Test setting the area."""
ellipse = Ellipse(a, b)
original_area = ellipse.area
ellipse.area = area
assert ellipse.area == approx(area)
# Reset to original area
ellipse.area = original_area
assert ellipse.area == approx(original_area)
assert ellipse.a == approx(a)
assert ellipse.b == approx(b)
def test_inertia_tensor(a, b, center):
ellipse = Ellipse(a, b)
assert np.all(np.asarray(ellipse.planar_moments_inertia) >= 0)
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_eccentricity_ratio(a, k):
b = a * k
ellipse = Ellipse(a, b)
b, a = sorted([a, b])
expected = np.sqrt(1 - b**2 / a**2)
assert ellipse.eccentricity == pytest.approx(expected)
def test_eccentricity(a, b):
ellipse = Ellipse(a, b)
assert ellipse.eccentricity >= 0
def test_iq(a, b):
ellipse = Ellipse(a, b)
assert ellipse.iq <= 1
def test_area(a, b):
ellipse = Ellipse(1, 1)
ellipse.a = a
ellipse.b = b
assert ellipse.area == np.pi * a * b