def test_frame_rotations_for_mean_of_date():
ts = api.load.timescale()
t = ts.utc(2020, 11, 21)
p = ICRF((1.1, 1.2, 1.3), t=t)
lat, lon, distance1 = p.frame_latlon(true_equator_and_equinox_of_date)
# Verify that the frame_latlon() coordinates match those from the
# more conventional radec() call.
ra, dec, distance2 = p.radec(epoch='date')
assert abs(lat.arcseconds() - dec.arcseconds()) < 1e-6
assert abs(lon.arcseconds() - ra.arcseconds()) < 1e-6
assert abs(distance1.au - distance2.au) < 1e-15
# Now that we know the coordinates are good, we can use them to
# rebuild a trusted x,y,z vector with which to test frame_xyz().
x1, y1, z1 = from_spherical(distance1.au, lat.radians, lon.radians)
x2, y2, z2 = p.frame_xyz(true_equator_and_equinox_of_date).au
assert abs(x1 - x2) < 1e-15
assert abs(y1 - y2) < 1e-15
assert abs(z1 - z2) < 1e-15
def test_right():
dx, dy, dz = from_spherical(1, 0, 0) - [1, 0, 0]
assert abs(dx) < 1e-15
assert abs(dy) < 1e-15
assert abs(dz) < 1e-15
def test_left_up():
sqrt2 = 0.5**0.5
dx, dy, dz = from_spherical(1, 0.125 * tau, 0.5 * tau) - [-sqrt2, 0, sqrt2]
assert abs(dx) < 1e-15
assert abs(dy) < 1e-15
assert abs(dz) < 1e-15
def test_up():
dx, dy, dz = from_spherical(1, 0.25 * tau, 0) - [0, 0, 1]
assert abs(dx) < 1e-15
assert abs(dy) < 1e-15
assert abs(dz) < 1e-15
def test_down():
dx, dy, dz = from_spherical(1, 0, 0.75 * tau) - [0, -1, 0]
assert abs(dx) < 1e-15
assert abs(dy) < 1e-15
assert abs(dz) < 1e-15