Enhancement: Implement pytest unit tests, coverage, and Continous Integration

[abhiTronix]

Detailed Description

This issue will track implementation of pytest unit tests, coverage reports, flake8 tests, and automated CI validation on different environments.

Roadmap

• Add comprehensive pytest unit tests for each case.
• Add Bash script for dataset download for unit test.
• Add GitHub Action CI support for Linux-based Testing Envs.
• Add Appveyor CI support for Windows-based Testing Envs.
• Add Azure Pipeline CI support for MacOS-based Testing Envs.
• Add and configure various yamls.
  • auto-handle prerequisites installation, testing, and coverage report uploading.
• Add code coverage through codecov measures tests effectiveness.
• Add flake8 testing to discover any anomalies in code.
• Add badges to Readme.md
• Fix any related bugs.

Context

This issue will oversee implementation of pytest unit tests, coverage, and Continous Integration essential for stable working of Deffcode on different OSes and environments.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)