Updating tests and CategoricalImputer to correctly intepret default fill_value

Author: Brendan Herger

sklearn_pandas/categorical_imputer.py

@@ -73,12 +73,6 @@ def __init__(
                 'Strategy {0} not in {1}'.format(self.strategy, strategies)
             )
 
-        if self.strategy == 'constant' and self.fill_value is None:
-            raise ValueError(
-                'Please specify a value for \'fill_value\''
-                'when using the constant strategy.'
-            )
-
     def fit(self, X, y=None):
         """
 

tests/test_categorical_imputer.py

@@ -156,14 +156,6 @@ def test_custom_replacement(replacement_value, input_type):
     assert (Xt == ['a', replacement_value, 'b', 'b']).all()
 
 
-def test_missing_replacement():
-    """
-    Raise error if no replacement value specified and strategy='constant'
-    """
-    with pytest.raises(ValueError):
-        CategoricalImputer(strategy="constant")
-
-
 def test_invalid_strategy():
     """
     Raise an error if an invalid strategy is entered