Basic test_api file. Update documentation

.pre-commit-config.yaml

@@ -6,8 +6,9 @@ repos:
     -   id: end-of-file-fixer
     -   id: check-yaml
     -   id: debug-statements
-    -   id: name-tests-test
     -   id: requirements-txt-fixer
+    -   id: name-tests-test
+        args: [--pytest-test-first]
 -   repo: https://github.com/asottile/setup-cfg-fmt
     rev: v2.5.0
     hooks:

CONTRIBUTING.md

@@ -13,3 +13,12 @@ pre-commit install
 ```
 
 Now `pre-commit` will run automatically on `git commit` :)
+
+## Write and run tests
+
+You should create unit tests for each new feature or API change (see [test_api.py](https://github.com/openfoodfacts/open-prices/blob/main/tests/test_api.py)).
+
+To run tests, just launch:
+```bash
+pytest
+```

tests/test_api.py

@@ -0,0 +1,11 @@
+from fastapi.testclient import TestClient
+
+from app.api import app
+
+
+client = TestClient(app)
+
+
+def test_hello():
+    response = client.get("/")
+    assert response.status_code == 200