Provides a dummy cache object for testing or placeholder purposes.

Signals that the object is a test double/cache stub that intentionally ignores inputs and returns no effect.

Used when a real cache is not needed, e.g., during unit testing to isolate dependencies, or as a placeholder in prototype code.

Unit testing Test doubles Stubbing dependencies Prototyping Mocking external caches

type(class_name, (), {'method_name': lambda self, *args: default_return})

type('FakeCache', (), {'get': lambda self, key: None, 'set': lambda self, key, value: None})

class_name method_name:get method_name:set return_value:None

• FakeCache mock stub test mock object unittest dependency injection

• unittest.mock.Mock collections.defaultdict simple dict lambda: None

Failing to include self parameter in lambda Returning a value when None is expected causing test failures Forgetting to bind methods to instance leading to TypeError Using mutable default arguments incorrectly

types.SimpleNamespace collections.namedtuple unittest.mock.MagicMock hand‑crafted class with explicit methods

May be mistaken for a functional cache, leading to silent bugs if caching behavior is expected.

• test doubles / mock objects

The get and set methods deliberately ignore their arguments and always return None, making the object a no‑op stub.

Communicates intentional absence of caching behavior, signaling a test double or placeholder to readers of the code.

Fake cache that does nothing

Useful for quick stubs; for more complex behavior consider unittest.mock.Mock or a real caching library like functools.lru_cache.

Replace with unittest.mock.Mock for flexible behavior, or use functools.lru_cache for a lightweight real cache.