fix more tests

Author: jorisvandenbossche

pandas/core/indexes/base.py

@@ -5453,9 +5453,10 @@ def equals(self, other: Any) -> bool:
 
         if (
             isinstance(self.dtype, StringDtype)
-            and self.dtype.storage == "pyarrow_numpy"
+            and self.dtype.na_value is np.nan
             and other.dtype != self.dtype
         ):
+            # TODO(infer_string) can we avoid this special case?
             # special case for object behavior
             return other.equals(self.astype(object))
 

pandas/tests/strings/__init__.py

@@ -7,7 +7,7 @@
 
 def _convert_na_value(ser, expected):
     if ser.dtype != object:
-        if ser.dtype.storage == "pyarrow_numpy":
+        if ser.dtype.na_value is np.nan:
             expected = expected.fillna(np.nan)
         else:
             # GH#18463