Add some tests for ways users can change or shadow globals and builtins.
diff --git a/Lib/test/support.py b/Lib/test/support.py
index a05f420..28f7e27 100644
--- a/Lib/test/support.py
+++ b/Lib/test/support.py
@@ -30,7 +30,8 @@
"run_with_locale",
"set_memlimit", "bigmemtest", "bigaddrspacetest", "BasicTestRunner",
"run_unittest", "run_doctest", "threading_setup", "threading_cleanup",
- "reap_children", "cpython_only", "check_impl_detail", "get_attribute"]
+ "reap_children", "cpython_only", "check_impl_detail", "get_attribute",
+ "swap_item", "swap_attr"]
class Error(Exception):
"""Base class for regression test exceptions."""
@@ -1074,3 +1075,57 @@
break
except:
break
+
+@contextlib.contextmanager
+def swap_attr(obj, attr, new_val):
+ """Temporary swap out an attribute with a new object.
+
+ Usage:
+ with swap_attr(obj, "attr", 5):
+ ...
+
+ This will set obj.attr to 5 for the duration of the with: block,
+ restoring the old value at the end of the block. If `attr` doesn't
+ exist on `obj`, it will be created and then deleted at the end of the
+ block.
+ """
+ if hasattr(obj, attr):
+ real_val = getattr(obj, attr)
+ setattr(obj, attr, new_val)
+ try:
+ yield
+ finally:
+ setattr(obj, attr, real_val)
+ else:
+ setattr(obj, attr, new_val)
+ try:
+ yield
+ finally:
+ delattr(obj, attr)
+
+@contextlib.contextmanager
+def swap_item(obj, item, new_val):
+ """Temporary swap out an item with a new object.
+
+ Usage:
+ with swap_item(obj, "item", 5):
+ ...
+
+ This will set obj["item"] to 5 for the duration of the with: block,
+ restoring the old value at the end of the block. If `item` doesn't
+ exist on `obj`, it will be created and then deleted at the end of the
+ block.
+ """
+ if item in obj:
+ real_val = obj[item]
+ obj[item] = new_val
+ try:
+ yield
+ finally:
+ obj[item] = real_val
+ else:
+ obj[item] = new_val
+ try:
+ yield
+ finally:
+ del obj[item]