Ansible: How to unit test module without using `pytest`

by yaobin.wen

Ansible uses pytest for unit testing. Usually, one cannot test the run_module() function directly because it requires two things:

• stdin as AnsibleModule reads its input arguments from the standard input.
• exit_json() and fail_json() call sys.exit() which will cause the test program to exit.

Therefore, usually one can only test the functions that the Ansible module calls. But the patch_ansible_module() function makes it possible to test the Ansible module directly.

However, sometimes the project may not use pytest as the unit testing tool. Instead, the project may use Python’s built-in unittest module. In this case, we wouldn’t be able to use the function patch_ansible_module().

But I implemented this demo to show how to unit test an AnsibleModule in real mode and check mode using Python’s unittest module. Basically,

• Implement class MyAnsibleModule(AnsibleModuleBasic.AnsibleModule) in order to change the behaviors of exit_json() and fail_json() so, when called, they don’t actually quit the test program.
• Use mock to replace the real AnsibleModule with MyAnsibleModule.
• Set _ansible_check_mode in ansible.module_utils.basic._ANSIBLE_ARGS in order to use the check mode.

Go take a look at the code.