def test_pixel_to_world_correlation_matrix_celestial():
wcs = WCS(naxis=2)
wcs.wcs.ctype = 'RA---TAN', 'DEC--TAN'
wcs.wcs.set()
assert_equal(wcs.axis_correlation_matrix, [[1, 1], [1, 1]])
matrix, classes = _pixel_to_world_correlation_matrix(wcs)
assert_equal(matrix, [[1, 1]])
assert classes == [SkyCoord]
def test_pixel_to_world_correlation_matrix_spectral_cube_uncorrelated():
wcs = WCS(naxis=3)
wcs.wcs.ctype = 'RA---TAN', 'FREQ', 'DEC--TAN'
wcs.wcs.set()
assert_equal(wcs.axis_correlation_matrix, [[1, 0, 1], [0, 1, 0], [1, 0, 1]])
matrix, classes = _pixel_to_world_correlation_matrix(wcs)
assert_equal(matrix, [[1, 0, 1], [0, 1, 0]])
assert classes == [SkyCoord, Quantity]
