PyTest-API: Populate OpenAPI Examples from Python Tests
PyTest-API is an ASGI middleware that populates OpenAPI-Specification examples from pytest functions.
Installation
poetry add --dev pytest-api
How to use it:
Starting with test_main.py file:
from .main import spec
@spec.describe(route="/behavior-example/")
def test_example_body(client):
"""
GIVEN behavior in body
WHEN example behavior endpoint is called with POST method
THEN response with status 200 and body OK is returned
"""
assert client.post(
"/behavior-example/", json={"name": "behavior"},
headers={"spec-example": test_example_body.id}
).json() == {"message": "OK"}Impliment solution in /main.py file:
from fastapi import FastAPI
from pydantic import BaseModel
from pytest_api import ASGIMiddleware
app = FastAPI()
spec = ASGIMiddleware
app.add_middleware(spec)
app.openapi = spec.openapi_behaviors(app)
class Behavior(BaseModel):
name: str
@app.post("/behavior-example/")
async def example_body(behavior: Behavior):
return {"message": "OK"}Run FastAPI app:
poetry run uvicorn test_app.main:app --reloadOpen your browser to http://localhost:8000/docs#/ too find the doc string is populated into the description.
Implimentation Details
Under the hood the ASGIMiddleware uses the describe decorator to store the pytest function by its id:
def wrap_behavior(*args, **kwargs):
try:
BEHAVIORS[route]
except KeyError as e:
if route in e.args:
BEHAVIORS[route] = {str(id(func)): func}
BEHAVIORS[route][str(id(func))] = funcWhen pytest calls your API the SpecificationResponder is looking for the coresponding id in the headers of the request:
def handle_spec(self, headers):
behaviors = BEHAVIORS[self.path]
self.should_update_example = headers.get("spec-example", "") in behaviors
self.should_update_description = (
headers.get("spec-description", "") in behaviors
)
if self.should_update_example:
self.func = behaviors[headers.get("spec-example")]
elif self.should_update_description:
self.func = behaviors[headers.get("spec-description")]This is possible thanks to python's first-class functions i.e. Closure_(computer_programming).
