fix tests. Add whats new on the current changes

ciku · ciku · commit 10d0282fa909 · 2021-11-11T20:30:58.000+03:00
diff --git a/doc/whats_new/v1.1.rst b/doc/whats_new/v1.1.rst
@@ -120,6 +120,7 @@ Changelog
   A warning will always be raised upon the removal of empty columns.
   :pr:`21448` by :user:`Oleh Kozynets <OlehKSS>` and
   :user:`Christian Ritter <chritter>`.
+  :user:`Christian Ritter <chritter>.
 
 - |Fix| Fix a bug in :class:`linear_model.RidgeClassifierCV` where the method
   `predict` was performing an `argmax` on the scores obtained from
@@ -173,6 +174,12 @@ Changelog
   instead of `__init__`.
   :pr:`21434` by :user:`Krum Arnaudov <krumeto>`.
 
+
+:mod: `sklearn.decomposition.KernelPCA`
+..........................
+-[Fix] :class:`decomposition.KernelPCA` now validates input parameters in `fit` instead of `__init__`
+  :pr:`21567` by :user: `Maggie Chege <MaggieChege>`
+
 :mod:`sklearn.svm`
 ..................
 
diff --git a/sklearn/decomposition/_kernel_pca.py b/sklearn/decomposition/_kernel_pca.py
@@ -427,14 +427,13 @@ def fit(self, X, y=None):
         self : object
             Returns the instance itself.
         """
+        if self.fit_inverse_transform and self.kernel == "precomputed":
+            raise ValueError("Cannot fit_inverse_transform with a precomputed kernel.")
         X = self._validate_data(X, accept_sparse="csr", copy=self.copy_X)
         self._centerer = KernelCenterer()
         K = self._get_kernel(X)
         self._fit_transform(K)
 
-        if self.fit_inverse_transform and self.kernel == "precomputed":
-            raise ValueError("Cannot fit_inverse_transform with a precomputed kernel.")
-
         if self.fit_inverse_transform:
             # no need to use the kernel to transform X, use shortcut expression
             X_transformed = self.eigenvectors_ * np.sqrt(self.eigenvalues_)
diff --git a/sklearn/decomposition/tests/test_kernel_pca.py b/sklearn/decomposition/tests/test_kernel_pca.py
@@ -79,7 +79,10 @@ def test_kernel_pca_invalid_parameters():
     ValueError.
     """
     with pytest.raises(ValueError):
-        KernelPCA(10, fit_inverse_transform=True, kernel="precomputed")
+        estimator = KernelPCA(
+            n_components=10, fit_inverse_transform=True, kernel="precomputed"
+        )
+        estimator.fit(np.random.randn(10, 10))
 
 
 def test_kernel_pca_consistent_transform():
