TST: Add tests for mask with NA. (pandas-dev#60729)

Author: sanggon6107

pandas/tests/series/indexing/test_mask.py

@@ -67,3 +67,19 @@ def test_mask_inplace():
     rs = s.copy()
     rs.mask(cond, -s, inplace=True)
     tm.assert_series_equal(rs, s.mask(cond, -s))
+
+
+def test_mask_na():
+    # We should not be filling pd.NA. See GH#60729
+    series = Series([None, 1, 2, None, 3, 4, None])
+    series = series.convert_dtypes()
+    cond = series <= 2
+
+    maskres = series.mask(cond, -99)
+    whereres = series.where(~(cond), -99)
+
+    expected = Series([None, -99, -99, None, 3, 4, None])
+    expected = expected.convert_dtypes()
+
+    tm.assert_series_equal(maskres, expected)
+    tm.assert_series_equal(maskres, whereres)