Add tests

[uniqueg]

Is your feature request related to a problem? Please describe.
Add unit and/or integration tests.

This is a "meta" issue, please leave it open and do not assign yourself to it. Instead, please open up a new issue for any one particular test that you wish to implement and assign yourself for that issue. Make sure that the issue has the bh19 label and starts with the name "Test" and some descriptive label, e.g., for a unit test that could be the tested function's name.

If you implement a new type of test, please add link to it in section Examples below.

Please add any helpful context, background info, framework in section Additional context below.

Describe the solution you'd like

• Write unit tests for every function
• Write integration tests for:
  • accessibility of the app
  • availability and functionality of all its required external services (database, broker, worker)
  • availability and functionality of any internal services (error handler, authorization, logging, monitoring)
  • availability and functionality of all endpoints and all associated responses
  • entire use cases
  • interaction with TES service

Describe alternatives you've considered
N/A

Examples
pytest: https://github.com/elixir-europe/TEStribute/tree/dev/tests

Additional context
Many of the tests will require a WES client, such as this: elixir-europe/WES-cli

[fgypas]

List of tests that will speed up the development and deployment:

Based on WES-cli

• Get service info
• Post workflow and check if it's running
• Get run id and get status
• Check if authentication is working (we need one instance with and one without authentication)