Configure and implement Pytest

[arthurTemporim]

This issue aims to configure a unit tests tool.

Tasks:

• Define a test tool (probably pytest)
• Configure it locally
• Add tests to CI
• Add badge of project coverage
• Create the first test of the project

Is important too:

• Define how to make integration tests (very important to components usage). Moved to Configure integration tests #76
• Define how to make stress tests
• Define how to make load tests. Moved to Configure load tests #77

[arthurTemporim]

After a quick search I guess the best testing tool is pytest
This was the source that I used: PythonTestingToolsTaxonomy

[arthurTemporim]

The pytest organization of this project followed this tutorial:
Good Practices

[arthurTemporim]

To add the test coverage badge to this project is needed an action by the owner @ralphg6.
This project README has the needed steps codecov

1. Access codecov site and create an account (I made it using my GitHub account) codecov site
2. Agree with codecov terms
3. Add David project to codecov list
4. Use the generated token to link the badge
5. Add the codecov link to README

I suggest to first make this configuration in test branch and after everything works move it to develop and master.

[arthurTemporim]

Another option is to use this simple and awesome project to generate the badge image:
coverage-badge

After that is just needed to store the badge somewhere in the repository and link it to README.md, some more configurations must be needed in CI tools.

What do you think? 🤔

[ralphg6]

[![codecov](https://codecov.io/gh/ralphg6/david/branch/develop/graph/badge.svg)](https://codecov.io/gh/ralphg6/david)

[ralphg6]

I removed codecov integration why Codeclimate already is configurated and he to integrate with the Coverage.py and the integration already was configured.

@arthurTemporim for me, the task 'Add badge of project coverage' was completed by #74.