typemock: type safe mockingΒΆ


This library is still in Alpha. API and implementation could change, and functionality is also not complete.

The mocking tools in python are powerful, flexible and useful for building independent tests at various levels.

This flexibility is part of what is considered a strength of the python language, and possibly any dynamically typed language.

However, this flexibility comes at a cost. Type flexibility in particular.

It is possible to build mocks which do not conform to the actual behaviour or contract defined by the things they are mocking. Or, for them to be initially correct, and then to go out of sync with actual behaviour and for tests to remain green.

We do not have compile time protections for us doing things with/to things which do not align with the contracts they define and the clients of those contracts expect.

But, now we have type hints. And so, we can explicitly define the contracts of our objects, and, if we have done this, we can mock them in a type safe way as well. This is what this library aims to help achieve. Type safe mocking.

Used in conjunction with mypy, this should result in much more high fidelity independent tests.


typemock uses the typeguard library to do runtime type checking. Just wanted to give them credit, and make users of this library aware.