TST: Add test for complex categories GH#16399

Signed-off-by: Liang Yan <ckgppl_yan@sina.cn>

Author: liang3zy22

pandas/tests/dtypes/test_dtypes.py

@@ -1173,6 +1173,13 @@ def test_cast_string_to_complex():
     result = pd.DataFrame(["1.0+5j", "1.5-3j"]).astype(complex)
     tm.assert_frame_equal(result, expected)
 
+def test_categorical_complex():
+    result = pd.Categorical([1, 2 + 2j])
+    expected = pd.Categorical([1.0+0.0j, 2.0+2.0j])
+    tm.assert_categorical_equal(result, expected)
+    result = pd.Categorical([1, 2, 2 + 2j])
+    expected = pd.Categorical([1.0+0.0j, 2.0+0.0j, 2.0+2.0j])
+    tm.assert_categorical_equal(result, expected)
 
 def test_multi_column_dtype_assignment():
     # GH #27583