def test_whiten_error():
rng = np.random.RandomState(123)
m, n = 500, 4
X = rng.randn(m, n)
with pytest.raises(ValueError, match="method must be one of"):
Y, W = whiten_data(X, method="uniform")
def test_whiten(method, centre):
rng = np.random.RandomState(123)
m, n = 500, 4
X = rng.randn(m, n)
Y, W = whiten_data(X, centre=centre, method=method)
cov = Y.T @ Y
cov *= n / np.trace(cov)
# Y.T @ Y should be approximately an identity matrix
np.testing.assert_allclose(cov, np.eye(n), atol=1e-6)