diff --git a/pandas/tests/test_categorical.py b/pandas/tests/test_categorical.py
new file mode 100644
index 0000000000000..946ce25b7edd4
--- /dev/null
+++ b/pandas/tests/test_categorical.py
@@ -0,0 +1,22 @@
+import pandas as pd
+import unittest
+
+def series_fill(cat, ele):
+  if cat.dtype == 'object':
+      raise TypeError("Given DataFrame is not of category datatype. Please change it to category datatype.")
+  if ele not in cat.categories:
+    raise TypeError("Element not present in categories. Cannot be filled in series.")
+  ser = pd.Series(cat).fillna(ele)
+  filled = cat.fillna(ser)
+  return filled
+
+class Test_series_fill(unittest.TestCase):
+  
+  def test_series_fill(self):
+    self.assertCountEqual(series_fill(pd.Categorical(["A", "B", None]), "B"), ["A", "B", "B"])
+    self.assertCountEqual(series_fill(pd.Categorical(["1", "2", "3", None]), "2"), ["1", "2", "3", "2"])
+
+  def test_input_value(self):
+    self.assertRaises(TypeError, series_fill, True)
+
+unittest.main(argv=[''],verbosity=2, exit=False)
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