How to write and run unittest in python

Following shows simple and cleary way to write unittest in python, and how to run them before launching a fastapi project.

write a unittest

Suppose you have the following class in some_class.py

# some_class.py

class SomeClass:
    def get_dictionary(self):
        # Implementation of the function
        return {"key": "value"}  # Example dictionary

Then it is easy to write an unitttest file like the following “test_some_class.py” as:

# test_some_class.py

import unittest
from some_class import SomeClass

class TestSomeClass(unittest.TestCase):
    def setUp(self):
        # This method will be run before each test method
        self.obj = SomeClass()

    def test_get_dictionary(self):
        result = self.obj.get_dictionary()
        self.assertIsInstance(result, dict)  # Check if result is a dictionary

    # You can add more test methods here. They will all have access to self.obj

if __name__ == '__main__':
    unittest.main()

run your test jobs in a project

Now you have your unitttest setup, now how to you run the tests?
For example, you might have a fastapi project, but before deployment, you want to run some unittest.

my_fastapi_project/
│
├── src/
│   ├── some_class.py
│   └── test_some_class.py
│
└── main.py  # <-- Your FastAPI application entry point

Here is how you would run the tests using the standard unittest module:

# Navigate to the project directory
cd my_fastapi_project

# Run the unittests with discovery
python -m unittest discover src

If the tests are successful and you’re satisfied with the results, you can then start your FastAPI application:

# Start the FastAPI application
uvicorn main:app --reload

Alternatively, if you have pytest installed, which provides more features and a nicer output, you can run:

# Navigate to the project directory (if not already there)
cd my_fastapi_project

# Run the tests with pytest
pytest src

# Check If pytest is successful