Tests in this directory are compiled into the _testcapi extension. The main file for the extension is Modules/_testcapimodule.c, which calls `_PyTestCapi_Init_*` from these functions. General guideline when writing test code for C API. * Use Argument Clinic to minimise the amount of boilerplate code. * Add a newline between the argument spec and the docstring. * If a test description is needed, make sure the added docstring clearly and succinctly describes purpose of the function. * DRY, use the clone feature of Argument Clinic. * Try to avoid adding new interned strings; reuse existing parameter names if possible. Use the `as` feature of Argument Clinic to override the C variable name, if needed.