text: import pytest
  import warnings
  import numpy as np
  from numpy.testing import assert_array_almost_equal, assert_array_equal, assert_allclose
  
  from sklearn.datasets import load_linnerud
  from sklearn.cross_decomposition._pls import (
      _center_scale_xy,
      _get_first_singular_vectors_power_method,
      _get_first_singular_vectors_svd,
      _svd_flip_1d,
  )
  from sklearn.cross_decomposition import CCA
  from sklearn.cross_decomposition import PLSSVD, PLSRegression, PLSCanonical
  from sklearn.datasets import make_regression
  from sklearn.utils import check_random_state
  from sklearn.utils.extmath import svd_flip
  from sklearn.exceptions import ConvergenceWarning
  
  
  def assert_matrix_orthogonal(M):
      K = np.dot(M.T, M)
      assert_array_almost_equal(K, np.diag(np.diag(K)))
  
  
  def test_pls_canonical_basics():
      # Basic checks for PLSCanonical
      d = load_linnerud()
      X = d.data
      Y = d.target
  
      pls = PLSCanonical(n_components=X.shape[1])
      pls.fit(X, Y)
  
      assert_matrix_orthogonal(pls.x_weights_)
      assert_matrix_orthogonal(pls.y_weights_)
      assert_matrix_orthogonal(pls._x_scores)
      assert_matrix_orthogonal(pls._y_scores)
  
      # Check X = TP' and Y = UQ'
      T = pls._x_scores
      P = pls.x_loadings_
      U = pls._y_scores
      Q = pls.y_loadings_
      # Need to scale first
      Xc, Yc, x_mean, y_mean, x_std, y_std = _center_scale_xy(
          X.copy(), Y.copy(), scale=True
      )
      assert_array_almost_equal(Xc, np.dot(T, P.T))
      assert_array_almost_equal(Yc, np.dot(U, Q.T))
  
      # Check that rotations on training data lead to scores
      Xt = pls.transform(X)
      assert_array_almost_equal(Xt, pls._x_scores)
      Xt, Yt = pls.transform(X, Y)
      assert_array_almost_equal(Xt, pls._x_scores)
      assert_array_almost_equal(Yt, pls._y_scores)
  
      # Check that inverse_transform works
      X_back = pls.inverse_transform(Xt)
      assert_array_almost_equal(X_back, X)
      _, Y_back = pls.inverse_transform(Xt, Yt)
      assert_array_almost_equal(Y_back, Y)
  
  
  def test_sanity_check_pls_regression():
      # Sanity check for PLSRegression
      # The results were checked against the R-packages plspm, misOmics and pls
  
      d = load_linnerud()
      X = d.data
      Y = d.target
  
      pls = PLSRegression(n_components=X.shape[1])
      X_trans, _ = pls.fit_transform(X, Y)
  
      # FIXME: one would expect y_trans == pls.y_scores_ but this is not
      # the case.
      # xref: https://github.com/scikit-learn/scikit-learn/issues/22420
      assert_allclose(X_trans, pls.x_scores_)
  
      expected_x_weights = np.array(
          [
              [-0.61330704, -0.00443647, 0.78983213],
              [-0.74697144, -0.32172099, -0.58183269],
              [-0.25668686, 0.94682413, -0.19399983],
          ]
      )
  
      expected_x_loadings = np.array(
          [
              [-0.61470416, -0.24574278, 0.78983213],
              [-0.65625755, -0.14396183, -0.58183269],
              [-0.51733059, 1.00609417, -0.19399983],
          ]
      )
  
      expected_y_weights = np.array(
          [
              [+0.32456184, 0.29892183, 0.20316322],
              [+0.42439636, 0.61970543, 0.19320542],
              [-0.13143144, -0.26348971, -0.17092916],
          ]
      )
  
      expected_y_loadings = np.array(
          [
              [+0.32456184, 0.29892183, 0.20316322],
              [+0.42439636, 0.61970543, 0.19320542],
              [-0.13143144, -0.26348971, -0.17092916],
          ]
      )
  
      assert_array_almost_equal(np.abs(pls.x_loadings_), np.abs(expected_x_loadings))
      assert_array_almost_equal(np.abs(pls.x_weights_), np.abs(expected_x_weights))
      assert_array_almost_equal(np.abs(pls.y_loadings_), np.abs(expected_y_loadings))
      assert_array_almost_equal(np.abs(pls.y_weights_), np.abs(expected_y_weights))
  
      # The R / Python difference in the signs should be consistent across
      # loadings, weights, etc.
      x_loadings_sign_flip = np.sign(pls.x_loadings_ / expected_x_loadings)
      x_weights_sign_flip = np.sign(pls.x_weights_ / expected_x_weights)
      y_weights_sign_flip = np.sign(pls.y_weights_ / expected_y_weights)
      y_loadings_sign_flip = np.sign(pls.y_loadings_ / expected_y_loadings)
      assert_array_almost_equal(x_loadings_sign_flip, x_weights_sign_flip)
      assert_array_almost_equal(y_loadings_sign_flip, y_weights_sign_flip)
  
  
  def test_sanity_check_pls_regression_constant_column_Y():
      # Check behavior when the first column of Y is constant
      # The results are checked against a modified version of plsreg2
      # from the R-package plsdepot
      d = load_linnerud()
      X = d.data
      Y = d.target
      Y[:, 0] = 1
      pls = PLSRegression(n_components=X.shape[1])
      pls.fit(X, Y)
  
      expected_x_weights = np.array(
          [
              [-0.6273573, 0.007081799, 0.7786994],
              [-0.7493417, -0.277612681, -0.6011807],
              [-0.2119194, 0.960666981, -0.1794690],
          ]
      )
  
      expected_x_loadings = np.array(
          [
              [-0.6273512, -0.22464538, 0.7786994],
              [-0.6643156, -0.09871193, -0.6011807],
              [-0.5125877, 1.01407380, -0.1794690],
          ]
      )
  
      expected_y_loadings = np.array(
          [
              [0.0000000, 0.0000000, 0.0000000],
              [0.4357300, 0.5828479, 0.2174802],
              [-0.1353739, -0.2486423, -0.1810386],
          ]
      )
  
      assert_array_almost_equal(np.abs(expected_x_weights), np.abs(pls.x_weights_))
      assert_array_almost_equal(np.abs(expected_x_loadings), np.abs(pls.x_loadings_))
      # For the PLSRegression with default parameters, y_loadings == y_weights
      assert_array_almost_equal(np.abs(pls.y_loadings_), np.abs(expected_y_loadings))
      assert_array_almost_equal(np.abs(pls.y_weights_), np.abs(expected_y_loadings))
  
      x_loadings_sign_flip = np.sign(expected_x_loadings / pls.x_loadings_)
      x_weights_sign_flip = np.sign(expected_x_weights / pls.x_weights_)
      # we ignore the first full-zeros row for y
      y_loadings_sign_flip = np.sign(expected_y_loadings[1:] / pls.y_loadings_[1:])
  
      assert_array_equal(x_loadings_sign_flip, x_weights_sign_flip)
      assert_array_equal(x_loadings_sign_flip[1:], y_loadings_sign_flip)
  
  
  def test_sanity_check_pls_canonical():
      # Sanity check for PLSCanonical
      # The results were checked against the R-package plspm
  
      d = load_linnerud()
      X = d.data
      Y = d.target
  
      pls = PLSCanonical(n_components=X.shape[1])
      pls.fit(X, Y)
  
      expected_x_weights = np.array(
          [
              [-0.61330704, 0.25616119, -0.74715187],
              [-0.74697144, 0.11930791, 0.65406368],
              [-0.25668686, -0.95924297, -0.11817271],
          ]
      )
  
      expected_x_rotations = np.array(
          [
              [-0.61330704, 0.41591889, -0.62297525],
              [-0.74697144, 0.31388326, 0.77368233],
              [-0.25668686, -0.89237972, -0.24121788],
          ]
      )
  
      expected_y_weights = np.array(
          [
              [+0.58989127, 0.7890047, 0.1717553],
              [+0.77134053, -0.61351791, 0.16920272],
              [-0.23887670, -0.03267062, 0.97050016],
          ]
      )
  
      expected_y_rotations = np.array(
          [
              [+0.58989127, 0.7168115, 0.30665872],
              [+0.77134053, -0.70791757, 0.19786539],
              [-0.23887670, -0.00343595, 0.94162826],
          ]
      )
  
      assert_array_almost_equal(np.abs(pls.x_rotations_), np.abs(expected_x_rotations))
      assert_array_almost_equal(np.abs(pls.x_weights_), np.abs(expected_x_weights))
      assert_array_almost_equal(np.abs(pls.y_rotations_), np.abs(expected_y_rotations))
      assert_array_almost_equal(np.abs(pls.y_weights_), np.abs(expected_y_weights))
  
      x_rotations_sign_flip = np.sign(pls.x_rotations_ / expected_x_rotations)
      x_weights_sign_flip = np.sign(pls.x_weights_ / expected_x_weights)
      y_rotations_sign_flip = np.sign(pls.y_rotations_ / expected_y_rotations)
      y_weights_sign_flip = np.sign(pls.y_weights_ / expected_y_weights)
      assert_array_almost_equal(x_rotations_sign_flip, x_weights_sign_flip)
      assert_array_almost_equal(y_rotations_sign_flip, y_weights_sign_flip)
  
      assert_matrix_orthogonal(pls.x_weights_)
      assert_matrix_orthogonal(pls.y_weights_)
  
      assert_matrix_orthogonal(pls._x_scores)
      assert_matrix_orthogonal(pls._y_scores)
  
  
  def test_sanity_check_pls_canonical_random():
      # Sanity check for PLSCanonical on random data
      # The results were checked against the R-package plspm
      n = 500
      p_noise = 10
      q_noise = 5
      # 2 latents vars:
      rng = check_random_state(11)
      l1 = rng.normal(size=n)
      l2 = rng.normal(size=n)
      latents = np.array([l1, l1, l2, l2]).T
      X = latents + rng.normal(size=4 * n).reshape((n, 4))
      Y = latents + rng.normal(size=4 * n).reshape((n, 4))
      X = np.concatenate((X, rng.normal(size=p_noise * n).reshape(n, p_noise)), axis=1)
      Y = np.concatenate((Y, rng.normal(size=q_noise * n).reshape(n, q_noise)), axis=1)
  
      pls = PLSCanonical(n_components=3)
      pls.fit(X, Y)
  
      expected_x_weights = np.array(
          [
              [0.65803719, 0.19197924, 0.21769083],
              [0.7009113, 0.13303969, -0.15376699],
              [0.13528197, -0.68636408, 0.13856546],
              [0.16854574, -0.66788088, -0.12485304],
              [-0.03232333, -0.04189855, 0.40690153],
              [0.1148816, -0.09643158, 0.1613305],
              [0.04792138, -0.02384992, 0.17175319],
              [-0.06781, -0.01666137, -0.18556747],
              [-0.00266945, -0.00160224, 0.11893098],
              [-0.00849528, -0.07706095, 0.1570547],
              [-0.00949471, -0.02964127, 0.34657036],
              [-0.03572177, 0.0945091, 0.3414855],
              [0.05584937, -0.02028961, -0.57682568],
              [0.05744254, -0.01482333, -0.17431274],
          ]
      )
  
      expected_x_loadings = np.array(
          [
              [0.65649254, 0.1847647, 0.15270699],
              [0.67554234, 0.15237508, -0.09182247],
              [0.19219925, -0.67750975, 0.08673128],
              [0.2133631, -0.67034809, -0.08835483],
              [-0.03178912, -0.06668336, 0.43395268],
              [0.15684588, -0.13350241, 0.20578984],
              [0.03337736, -0.03807306, 0.09871553],
              [-0.06199844, 0.01559854, -0.1881785],
              [0.00406146, -0.00587025, 0.16413253],
              [-0.00374239, -0.05848466, 0.19140336],
              [0.00139214, -0.01033161, 0.32239136],
              [-0.05292828, 0.0953533, 0.31916881],
              [0.04031924, -0.01961045, -0.65174036],
              [0.06172484, -0.06597366, -0.1244497],
          ]
      )
  
      expected_y_weights = np.array(
          [
              [0.66101097, 0.18672553, 0.22826092],
              [0.69347861, 0.18463471, -0.23995597],
              [0.14462724, -0.66504085, 0.17082434],
              [0.22247955, -0.6932605, -0.09832993],
              [0.07035859, 0.00714283, 0.67810124],
              [0.07765351, -0.0105204, -0.44108074],
              [-0.00917056, 0.04322147, 0.10062478],
              [-0.01909512, 0.06182718, 0.28830475],
              [0.01756709, 0.04797666, 0.32225745],
          ]
      )
  
      expected_y_loadings = np.array(
          [
              [0.68568625, 0.1674376, 0.0969508],
              [0.68782064, 0.20375837, -0.1164448],
              [0.11712173, -0.68046903, 0.12001505],
              [0.17860457, -0.6798319, -0.05089681],
              [0.06265739, -0.0277703, 0.74729584],
              [0.0914178, 0.00403751, -0.5135078],
              [-0.02196918, -0.01377169, 0.09564505],
              [-0.03288952, 0.09039729, 0.31858973],
              [0.04287624, 0.05254676, 0.27836841],
          ]
      )
  
      assert_array_almost_equal(np.abs(pls.x_loadings_), np.abs(expected_x_loadings))
      assert_array_almost_equal(np.abs(pls.x_weights_), np.abs(expected_x_weights))
      assert_array_almost_equal(np.abs(pls.y_loadings_), np.abs(expected_y_loadings))
      assert_array_almost_equal(np.abs(pls.y_weights_), np.abs(expected_y_weights))
  
      x_loadings_sign_flip = np.sign(pls.x_loadings_ / expected_x_loadings)
      x_weights_sign_flip = np.sign(pls.x_weights_ / expected_x_weights)
      y_weights_sign_flip = np.sign(pls.y_weights_ / expected_y_weights)
      y_loadings_sign_flip = np.sign(pls.y_loadings_ / expected_y_loadings)
      assert_array_almost_equal(x_loadings_sign_flip, x_weights_sign_flip)
      assert_array_almost_equal(y_loadings_sign_flip, y_weights_sign_flip)
  
      assert_matrix_orthogonal(pls.x_weights_)
      assert_matrix_orthogonal(pls.y_weights_)
  
      assert_matrix_orthogonal(pls._x_scores)
      assert_matrix_orthogonal(pls._y_scores)
  
  
  def test_convergence_fail():
      # Make sure ConvergenceWarning is raised if max_iter is too small
      d = load_linnerud()
      X = d.data
      Y = d.target
      pls_nipals = PLSCanonical(n_components=X.shape[1], max_iter=2)
      with pytest.warns(ConvergenceWarning):
          pls_nipals.fit(X, Y)
  
  
  @pytest.mark.parametrize("Est", (PLSSVD, PLSRegression, PLSCanonical))
  def test_attibutes_shapes(Est):
      # Make sure attributes are of the correct shape depending on n_components
      d = load_linnerud()
      X = d.data
      Y = d.target
      n_components = 2
      pls = Est(n_components=n_components)
      pls.fit(X, Y)
      assert all(
          attr.shape[1] == n_components for attr in (pls.x_weights_, pls.y_weights_)
      )
  
  
  # TODO(1.3): remove the warning filter
  @pytest.mark.filterwarnings(
      "ignore:The attribute `coef_` will be transposed in version 1.3"
  )
  @pytest.mark.parametrize("Est", (PLSRegression, PLSCanonical, CCA))
  def test_univariate_equivalence(Est):
      # Ensure 2D Y with 1 column is equivalent to 1D Y
      d = load_linnerud()
      X = d.data
      Y = d.target
  
      est = Est(n_components=1)
      one_d_coeff = est.fit(X, Y[:, 0]).coef_
      two_d_coeff = est.fit(X, Y[:, :1]).coef_
  
      assert one_d_coeff.shape == two_d_coeff.shape
      assert_array_almost_equal(one_d_coeff, two_d_coeff)
  
  
  @pytest.mark.parametrize("Est", (PLSRegression, PLSCanonical, CCA, PLSSVD))
  def test_copy(Est):
      # check that the "copy" keyword works
      d = load_linnerud()
      X = d.data
      Y = d.target
      X_orig = X.copy()
  
      # copy=True won't modify inplace
      pls = Est(copy=True).fit(X, Y)
      assert_array_equal(X, X_orig)
  
      # copy=False will modify inplace
      with pytest.raises(AssertionError):
          Est(copy=False).fit(X, Y)
          assert_array_almost_equal(X, X_orig)
  
      if Est is PLSSVD:
          return  # PLSSVD does not support copy param in predict or transform
  
      X_orig = X.copy()
      with pytest.raises(AssertionError):
          pls.transform(X, Y, copy=False),
          assert_array_almost_equal(X, X_orig)
  
      X_orig = X.copy()
      with pytest.raises(AssertionError):
          pls.predict(X, copy=False),
          assert_array_almost_equal(X, X_orig)
  
      # Make sure copy=True gives same transform and predictions as predict=False
      assert_array_almost_equal(
          pls.transform(X, Y, copy=True), pls.transform(X.copy(), Y.copy(), copy=False)
      )
      assert_array_almost_equal(
          pls.predict(X, copy=True), pls.predict(X.copy(), copy=False)
      )
  
  
  def _generate_test_scale_and_stability_datasets():
      """Generate dataset for test_scale_and_stability"""
      # dataset for non-regression 7818
      rng = np.random.RandomState(0)
      n_samples = 1000
      n_targets = 5
      n_features = 10
      Q = rng.randn(n_targets, n_features)
      Y = rng.randn(n_samples, n_targets)
      X = np.dot(Y, Q) + 2 * rng.randn(n_samples, n_features) + 1
      X *= 1000
      yield X, Y
  
      # Data set where one of the features is constraint
      X, Y = load_linnerud(return_X_y=True)
      # causes X[:, -1].std() to be zero
      X[:, -1] = 1.0
      yield X, Y
  
      X = np.array([[0.0, 0.0, 1.0], [1.0, 0.0, 0.0], [2.0, 2.0, 2.0], [3.0, 5.0, 4.0]])
      Y = np.array([[0.1, -0.2], [0.9, 1.1], [6.2, 5.9], [11.9, 12.3]])
      yield X, Y
  
      # Seeds that provide a non-regression test for #18746, where CCA fails
      seeds = [530, 741]
      for seed in seeds:
          rng = np.random.RandomState(seed)
          X = rng.randn(4, 3)
          Y = rng.randn(4, 2)
          yield X, Y
  
  
  @pytest.mark.parametrize("Est", (CCA, PLSCanonical, PLSRegression, PLSSVD))
  @pytest.mark.parametrize("X, Y", _generate_test_scale_and_stability_datasets())
  def test_scale_and_stability(Est, X, Y):
      """scale=True is equivalent to scale=False on centered/scaled data
      This allows to check numerical stability over platforms as well"""
  
      X_s, Y_s, *_ = _center_scale_xy(X, Y)
  
      X_score, Y_score = Est(scale=True).fit_transform(X, Y)
      X_s_score, Y_s_score = Est(scale=False).fit_transform(X_s, Y_s)
  
      assert_allclose(X_s_score, X_score, atol=1e-4)
      assert_allclose(Y_s_score, Y_score, atol=1e-4)
  
  
  @pytest.mark.parametrize("Est", (PLSSVD, PLSCanonical, CCA))
  @pytest.mark.parametrize(
      "n_components, err_type, err_msg",
      [
          (0, ValueError, "n_components == 0, must be >= 1."),
          (4, ValueError, "n_components == 4, must be <= 3."),
          (
              2.0,
              TypeError,
              "n_components must be an instance of int",
          ),
      ],
  )
  def test_n_components_bounds(Est, n_components, err_type, err_msg):
      """Check the validation of `n_components` for `PLS` regressors."""
      rng = np.random.RandomState(0)
      X = rng.randn(10, 5)
      Y = rng.randn(10, 3)
      est = Est(n_components=n_components)
      with pytest.raises(err_type, match=err_msg):
          est.fit(X, Y)
  
  
  @pytest.mark.parametrize(
      "n_components, err_type, err_msg",
      [
          (0, ValueError, "n_components == 0, must be >= 1."),
          (6, ValueError, "n_components == 6, must be <= 5."),
          (
              2.0,
              TypeError,
              "n_components must be an instance of int",
          ),
      ],
  )
  def test_n_components_bounds_pls_regression(n_components, err_type, err_msg):
      """Check the validation of `n_components` for `PLSRegression`."""
      rng = np.random.RandomState(0)
      X = rng.randn(10, 5)
      Y = rng.randn(10, 3)
      est = PLSRegression(n_components=n_components)
      with pytest.raises(err_type, match=err_msg):
          est.fit(X, Y)
  
  
  @pytest.mark.parametrize("n_samples, n_features", [(100, 10), (100, 200)])
  @pytest.mark.parametrize("seed", range(10))
  def test_singular_value_helpers(n_samples, n_features, seed):
      # Make sure SVD and power method give approximately the same results
      X, Y = make_regression(n_samples, n_features, n_targets=5, random_state=seed)
      u1, v1, _ = _get_first_singular_vectors_power_method(X, Y, norm_y_weights=True)
      u2, v2 = _get_first_singular_vectors_svd(X, Y)
  
      _svd_flip_1d(u1, v1)
      _svd_flip_1d(u2, v2)
  
      rtol = 1e-1
      assert_allclose(u1, u2, rtol=rtol)
      assert_allclose(v1, v2, rtol=rtol)
  
  
  def test_one_component_equivalence():
      # PLSSVD, PLSRegression and PLSCanonical should all be equivalent when
      # n_components is 1
      X, Y = make_regression(100, 10, n_targets=5, random_state=0)
      svd = PLSSVD(n_components=1).fit(X, Y).transform(X)
      reg = PLSRegression(n_components=1).fit(X, Y).transform(X)
      canonical = PLSCanonical(n_components=1).fit(X, Y).transform(X)
  
      assert_allclose(svd, reg, rtol=1e-2)
      assert_allclose(svd, canonical, rtol=1e-2)
  
  
  def test_svd_flip_1d():
      # Make sure svd_flip_1d is equivalent to svd_flip
      u = np.array([1, -4, 2])
      v = np.array([1, 2, 3])
  
      u_expected, v_expected = svd_flip(u.reshape(-1, 1), v.reshape(1, -1))
      _svd_flip_1d(u, v)  # inplace
  
      assert_allclose(u, u_expected.ravel())
      assert_allclose(u, [-1, 4, -2])
  
      assert_allclose(v, v_expected.ravel())
      assert_allclose(v, [-1, -2, -3])
  
  
  def test_loadings_converges():
      """Test that CCA converges. Non-regression test for #19549."""
      X, y = make_regression(n_samples=200, n_features=20, n_targets=20, random_state=20)
  
      cca = CCA(n_components=10, max_iter=500)
  
      with warnings.catch_warnings():
          warnings.simplefilter("error", ConvergenceWarning)
  
          cca.fit(X, y)
  
      # Loadings converges to reasonable values
      assert np.all(np.abs(cca.x_loadings_) < 1)
  
  
  def test_pls_constant_y():
      """Checks warning when y is constant. Non-regression test for #19831"""
      rng = np.random.RandomState(42)
      x = rng.rand(100, 3)
      y = np.zeros(100)
  
      pls = PLSRegression()
  
      msg = "Y residual is constant at iteration"
      with pytest.warns(UserWarning, match=msg):
          pls.fit(x, y)
  
      assert_allclose(pls.x_rotations_, 0)
  
  
  @pytest.mark.parametrize("PLSEstimator", [PLSRegression, PLSCanonical, CCA])
  def test_pls_coef_shape(PLSEstimator):
      """Check the shape of `coef_` attribute.
  
      Non-regression test for:
      https://github.com/scikit-learn/scikit-learn/issues/12410
      """
      d = load_linnerud()
      X = d.data
      Y = d.target
  
      pls = PLSEstimator(copy=True).fit(X, Y)
  
      # TODO(1.3): remove the warning check
      warning_msg = "The attribute `coef_` will be transposed in version 1.3"
      with pytest.warns(FutureWarning, match=warning_msg):
          assert pls.coef_.shape == (X.shape[1], Y.shape[1])
  
      # Next accesses do not warn
      with warnings.catch_warnings():
          warnings.simplefilter("error", FutureWarning)
          pls.coef_
  
      # TODO(1.3): rename `_coef_` to `coef_`
      assert pls._coef_.shape == (Y.shape[1], X.shape[1])
  
  
  # TODO (1.3): remove the filterwarnings and adapt the dot product between `X_trans` and
  # `pls.coef_`
  @pytest.mark.filterwarnings("ignore:The attribute `coef_` will be transposed")
  @pytest.mark.parametrize("scale", [True, False])
  @pytest.mark.parametrize("PLSEstimator", [PLSRegression, PLSCanonical, CCA])
  def test_pls_prediction(PLSEstimator, scale):
      """Check the behaviour of the prediction function."""
      d = load_linnerud()
      X = d.data
      Y = d.target
  
      pls = PLSEstimator(copy=True, scale=scale).fit(X, Y)
      Y_pred = pls.predict(X, copy=True)
  
      y_mean = Y.mean(axis=0)
      X_trans = X - X.mean(axis=0)
      if scale:
          X_trans /= X.std(axis=0, ddof=1)
  
      assert_allclose(pls.intercept_, y_mean)
      assert_allclose(Y_pred, X_trans @ pls.coef_ + pls.intercept_)
  
  
  @pytest.mark.parametrize("Klass", [CCA, PLSSVD, PLSRegression, PLSCanonical])
  def test_pls_feature_names_out(Klass):
      """Check `get_feature_names_out` cross_decomposition module."""
      X, Y = load_linnerud(return_X_y=True)
  
      est = Klass().fit(X, Y)
      names_out = est.get_feature_names_out()
  
      class_name_lower = Klass.__name__.lower()
      expected_names_out = np.array(
          [f"{class_name_lower}{i}" for i in range(est.x_weights_.shape[1])],
          dtype=object,
      )
      assert_array_equal(names_out, expected_names_out)
  