Python Unit Testing | FastAPI with Pytest Tutorial (fast & easy)

[@laszlomagyar3156]

The quality of your content is amazing! Keep up the good work!

[@codingwithroby]

I’m so glad you enjoy it 🙂

[@vatsal_gamit]

This is my first video on tests in python and its worth watching !! Keep doing the great work man!! 🙌🏼

[@codingwithroby]

Thanks, will do!

[@prasenjitgiri919]

are you runnig the main,py before running the test ? and what if the main.py file reads from os environment variables - how do you handle it without running the main file? - btw, great video!

[@tenzingyatso5096]

Nice! Could you make the same with async test and test db (postgres)?

[@jordiprim2668]

One question: if I change de order in the tests does not work, I mean, when the test_create_todo() goes first, then the test_read_todos() returns one element, so assert response.json()==[] is not true. Yes, I know thant there is setup_function, but does not efect the response.json(). I check also with fixture(autouse=True) and nothing changes...Do you know something about that? Thanks. Jordi.

[@codingwithroby]

Hey there! Your issue is happening because we are not returning a new client each time. What you need to do is create a new @pytest.fixture and also return the TestClient. I think you'd want something like: from fastapi.testclient import TestClient import pytest from .main import app, todos @pytest.fixture(autouse=True) def client(): # Clear the todos before each test todos.clear() # Create a fresh client for each test return TestClient(app) # Remove the setup_function as we're using fixture now def test_read_todos(client): response = client.get("/") assert response.status_code == 200 assert response.json() == [] def test_create_todo(client): response = client.post("/", json={"name": "Buy groceries", "completed": False}) assert response.status_code == 200 assert response.json() == {"name": "Buy groceries", "completed": False} // ... existing code for other test functions ... -- Make sure you pass in client to each test function due to us now using a pytest fixture.

[@jordiprim2668]

@@codingwithroby I understant what you mean, but the same happends with your code. If I run the test (test_get_totes_imatges) (test_get_all_images in english) alone works, but if I run all the tests no. I'm not pretending you analize all the code for me, but here it is, just in case you are bored :p -----------------------tests------------------ import pytest from fastapi.testclient import TestClient from main import app from dades.dades import imatges_db import logging import json @pytest.fixture(autouse=True) def client(): imatges_db["imatges"].clear() imatges_db["imatges"] = ([ {"id_imatge": 1, "nom_fotograf": "Joan", "titol_imatge": "Lluna plena", "descripcio_imatge": "Vista espectacular de la lluna"}, {"id_imatge": 2, "nom_fotograf": "Pep", "titol_imatge": "Ciutat de nit", "descripcio_imatge": "Vista espectacular ciutat per la nit"}, {"id_imatge": 3, "nom_fotograf": "Maria", "titol_imatge": "Ciutat de dia", "descripcio_imatge": "Vista espectacular ciutat pel dia"}, {"id_imatge": 4, "nom_fotograf": "Miriam", "titol_imatge": "Ciutat al migdia", "descripcio_imatge": "Vista espectacular ciutat al migdia"} ]) return TestClient(app) # Tests def test_create_new_imatge(client): nova_imatge = { "id_imatge": 5, "nom_fotograf": "Anna", "titol_imatge": "Nova imatge", "descripcio_imatge": "Una descripció nova." } response = client.post("/nova_imatge", json=nova_imatge) assert response.status_code == 200 assert response.json() == nova_imatge def test_create_duplicate_imatge(client): nova_imatge = { "id_imatge": 1, "nom_fotograf": "Joan", "titol_imatge": "Lluna plena", "descripcio_imatge": "Vista espectacular de la lluna" } response = client.post("/nova_imatge", json=nova_imatge) assert response.status_code == 400 assert response.json()["detail"] == "Codi ja existeix" def test_get_totes_imatges(client): response = client.get("/totes_imatges") assert response.status_code == 200 logging.info("RESPONSE JSON......: %s", response.json()) assert response.json() == imatges_db["imatges"] -------------------------------------error or not error (if alone)---------------------------------------------------------- pytest -k "totes" ======================================================== test session starts ========================================================= platform linux -- Python 3.12.3, pytest-8.3.4, pluggy-1.5.0 rootdir: /home/jordi/Documents/fastapi/imatges_test_fakedb configfile: pyproject.toml plugins: asyncio-0.25.2, anyio-4.7.0 asyncio: mode=Mode.STRICT, asyncio_default_fixture_loop_scope=function collected 3 items / 2 deselected / 1 selected test_imatges.py . [100%] ================================================== 1 passed, 2 deselected in 0.31s =================================================== (venv) jordi@jordi-Lenovo-ThinkBook-15-IIL:~/Documents/fastapi/imatges_test_fakedb/app$ pytest -v ======================================================== test session starts ========================================================= platform linux -- Python 3.12.3, pytest-8.3.4, pluggy-1.5.0 -- /home/jordi/Documents/fastapi/imatges_test_fakedb/venv/bin/python cachedir: .pytest_cache rootdir: /home/jordi/Documents/fastapi/imatges_test_fakedb configfile: pyproject.toml plugins: asyncio-0.25.2, anyio-4.7.0 asyncio: mode=Mode.STRICT, asyncio_default_fixture_loop_scope=function collected 3 items test_imatges.py::test_create_new_imatge PASSED [ 33%] test_imatges.py::test_create_duplicate_imatge PASSED [ 66%] test_imatges.py::test_get_totes_imatges FAILED [100%] ============================================================== FAILURES ============================================================== _______________________________________________________ test_get_totes_imatges _______________________________________________________ client = def test_get_totes_imatges(client): response = client.get("/totes_imatges") assert response.status_code == 200 logging.info("RESPONSE JSON......: %s", response.json()) > assert response.json() == imatges_db["imatges"] E AssertionError: assert [{'descripcio...Nova imatge'}] == [{'descripcio...t al migdia'}] E E Left contains one more item: {'descripcio_imatge': 'Una descripció nova.', 'id_imatge': 5, 'nom_fotograf': 'Anna', 'titol_imatge': 'Nova imatge'} E E Full diff: E [ E { E 'descripcio_imatge': 'Vista espectacular de la lluna',... E E ...Full output truncated (29 lines hidden), use '-vv' to show test_imatges.py:48: AssertionError ====================================================== short test summary info ======================================================= FAILED test_imatges.py::test_get_totes_imatges - AssertionError: assert [{'descripcio...Nova imatge'}] == [{'descripcio...t al migdia'}] ==================================================== 1 failed, 2 passed in 0.33s ============== Even if you analize my code or not I love your videos. I will change the order and thats it. Thanks for your help Eric!

[@Ruthwikranganathbethapudi]

How to unit test a FastAPI which is connected to Sqlite?

[@h3ct0rjs]

Thanks for this, have you test Tavern which can be used to run this test to using yaml and python ?

[@codingwithroby]

Oh interesting - I have never seen this before.

[@davidinawe791]

Hello. I have a question for fastapi testing with pytest and if someone could help me it would be very much appreciated! Essentially, what I need to do within my test is to simulate a server restart. But I do not understand how the server is actually started in pytest. We are running our API with hypercorn. Hypercorns serv() function in our main.py takes the app as a parameter and from my understanding runs the server like you normally would with "hypercorn main:app" by just running the main.py. I just don't understand how the server is actually started with pytest. All we do in pytest (same as in this video) is to define the TestClient, but from my understanding the TestClient is only the one ACCESSING the server that is already running. Therfore I don't know how I could simulate a restart of the server in pytest (like stopping and restarting the execution of "hypercorn main:app" in cmd). Could anyone help me out here and tell me what I am misunderstanding?

[@zeldacamila]

How to unit test a FastAPI which is connected to postgresql, on a CI environment (using github actions)??

[@codingwithroby]

Same way - I'd suggest use SQLite3 and create a separate testing database and not use a production database like PostgreSQL or MySQL

[@DhavalAhir10]

Ohhh, I thought pytest is only for Django based project. In Django we used Rq Worker or Celery. What it is in fastapi?

[@codingwithroby]

Celery often times. You can use whatever you'd like!

[@DhavalAhir10]

@@codingwithroby Thanks :)

[@amadzarak7746]

Great vid!

[@codingwithroby]

Thank you sir!

[@adithyayelloju8296]

When test cases become larger, How to refactor them?

[@codingwithroby]

Structure by business functionality. If you are testing more than 1 thing, break it into two tests.

[@hemantgiri2377]

sir, please make a video on fastapi with mvc architecture with celery and and redis.

[@codingwithroby]

Not a bad idea 🙂

[@nuri3029]

Great! Thank you

[@codingwithroby]

You’re welcome! I am glad you found value 🙂

[@CodingStudio]

but this is not unittesting? this is integration tests?

[@codingwithroby]

Well, you are not completely wrong. This would be considered integration testing but we do not really have a service layer here so it incorporates them both.

[@AlexanderLindholm-z1q]

You didn't test status code 400

[@codingwithroby]

I must have forgotten, feel free to test 400 on your side!