fix test cases which assumed mangled nans

Author: realead

pandas/tests/base/test_value_counts.py

@@ -287,5 +287,5 @@ def test_value_counts_with_nan(dropna, index_or_series):
     if dropna is True:
         expected = Series([1], index=[True])
     else:
-        expected = Series([2, 1], index=[pd.NA, True])
+        expected = Series([1, 1, 1], index=[True, pd.NA, np.nan])
     tm.assert_series_equal(res, expected)

pandas/tests/libs/test_hashtable.py

@@ -462,13 +462,10 @@ def test_mode_stable(self, dtype, type_suffix, writable):
 
 
 def test_modes_with_nans():
-    # GH39007
-    values = np.array([True, pd.NA, np.nan], dtype=np.object_)
-    # pd.Na and np.nan will have the same representative: np.nan
-    # thus we have 2 nans and 1 True
+    # GH42688, nans aren't mangled
+    values = np.array([True, pd.NA, np.nan, pd.NA, np.nan], dtype=np.object_)
     modes = ht.mode(values, False)
-    assert modes.size == 1
-    assert np.isnan(modes[0])
+    assert modes.size == 2
 
 
 @pytest.mark.parametrize(