TST: Added tests to test Deprecation warning

Author: MechCoder

sklearn/linear_model/coordinate_descent.py

@@ -712,7 +712,7 @@ def fit(self, X, y):
                           "estimator", stacklevel=2)
 
         if self.precompute == 'auto':
-            warnings.warn("Setting precompute to 'auto', has found to be "
+            warnings.warn("Setting precompute to 'auto', was found to be "
                           "slower even when n_samples > n_features. Hence "
                           "it will be removed in 0.18.",
                           DeprecationWarning, stacklevel=2)
@@ -1217,6 +1217,7 @@ def fit(self, X, y):
         model.alpha = best_alpha
         model.l1_ratio = best_l1_ratio
         model.copy_X = copy_X
+        model.precompute = False
         model.fit(X, y)
         if not hasattr(self, 'l1_ratio'):
             del self.l1_ratio_

sklearn/linear_model/tests/test_coordinate_descent.py

@@ -562,6 +562,18 @@ def test_random_descent():
     assert_raises(ValueError, clf_random.fit, X, y)
 
 
+def test_deprection_precompute_enet():
+    """
+    Test that setting precompute="auto" gives a Deprecation Warning.
+    """
+
+    X, y, _, _ = build_dataset(n_samples=20, n_features=10)
+    clf = ElasticNet(precompute="auto")
+    assert_warns(DeprecationWarning, clf.fit, X, y)
+    clf = Lasso(precompute="auto")
+    assert_warns(DeprecationWarning, clf.fit, X, y)
+
+
 if __name__ == '__main__':
     import nose
     nose.runmodule()