Rewrite sigfox unittest tests to pytest style test functions

[MartinHjelmare]

Problem

The sigfox integration still contains unittest.TestCase based unit tests. We want to rewrite them to standalone pytest test functions.

Background

The Home Assistant core standard is to write tests as standalone pytest test functions. We still have some old tests that are based on unittest.TestCase. We want all these tests to be rewritten as pytest test functions.

Here are the docs for pytest: https://docs.pytest.org/en/stable/

Here's an example of an async pytest test function in Home Assistant core:

https://github.com/home-assistant/core/blob/4cce724473233d4fb32c08bd251940b1ce2ba570/tests/components/tradfri/test_light.py#L156-L176

There are many pytest fixtures to help writing the tests. See:

• https://docs.pytest.org/en/stable/reference.html#fixtures
• https://github.com/home-assistant/core/blob/dev/tests/conftest.py
• The most common fixture to use is hass which will set up a HomeAssistant instance and start it.

Here's an example of a pull request that rewrote a module of unittest.TestCase tests to standalone pytest test functions: https://github.com/home-assistant/core/pull/40749

Here's an example command to run a single test module with pytest inside tox on Python 3.8:

tox -e py38 -- --cov-report term-missing --cov=homeassistant.components.command_line.switch tests/components/command_line/test_switch.py

It will print coverage information with lines that are missing coverage.

Prerequisites

• A working development environment.

Task

• Rewrite the tests one module at a time and submit the changes as a pull request to this repository.
• We want to limit the change scope to a single module to not have the pull request be too long, which would take longer time to review.
• Remember to reference this issue in your pull request, but don't close or fix the issue until all tests for the integration are updated.

[frangiz]

I can take a look into this one.