test for warning

Author: TomAugspurger

pandas/core/internals/blocks.py

@@ -1960,7 +1960,7 @@ def formatting_values(self):
                 "'ExtensionArray._formatting_values' is deprecated. "
                 "Specify 'ExtensionArray._formatter' instead."
             )
-            warnings.warn(msg, FutureWarning)
+            warnings.warn(msg, FutureWarning, stacklevel=10)
             return self.values._formatting_values()
 
         # the future implementation (and current, if not overrode)

pandas/tests/extension/decimal/test_decimal.py

@@ -202,7 +202,8 @@ class TestSetitem(BaseDecimal, base.BaseSetitemTests):
 
 
 class TestPrinting(BaseDecimal, base.BasePrintingTests):
-    pass
+    pytestmark = pytest.mark.skipif(compat.PY2,
+                                    reason="Unhashble dtype in Py2.")
 
 
 # TODO(extension)
@@ -384,3 +385,14 @@ def test_divmod_array(reverse, expected_div, expected_mod):
 
     tm.assert_extension_array_equal(div, expected_div)
     tm.assert_extension_array_equal(mod, expected_mod)
+
+
+def test_formatting_values_deprecated():
+    class DecimalArray2(DecimalArray):
+        def _formatting_values(self):
+            return np.array(self)
+
+    ser = pd.Series(DecimalArray2([decimal.Decimal('1.0')]))
+
+    with tm.assert_produces_warning(FutureWarning):
+        repr(ser)