Add unit-tests and initialises integration-test

[NeerajGartia21]

This PR adds unit-tests and initialises integration-tests.

Proposed folder structure :

--- tests
      |---integration
      |---unit
            |---test_suite_route.py
                  .....
      |---utils
            |---mocker.py
                 .....
      ---conftest.py

In this PR :

• pytest is used for unit-testing.
• pytest-mock is used for mocking dependencies.

Next Tasks :

• Adding Integration-tests.
• Adding CI for GitHub actions.

Note- Since it is good to have atomic commits, I will be adding unit-tests for different components in separate commits.

[kamoltat]

Please also add unit test for a function in src/services/kill.py. Please sign your commit using git commit -s. Also please drop the changes you have made on existing code, if you want to change something then, please file a separate PR. We only ask you to add unit-test in the assignment. 🙂

[kamoltat]

Please rebase.