u/Mysterious-Aerie4808

Building signup/login in FastAPI is not that hard.

The harder part is testing the cases people usually skip:

wrong password
duplicate email
expired access token
refresh token reuse
protected route without token
user accessing another user’s resource
deleted user still holding a token

The last one is especially easy to miss.

Your endpoint might verify the JWT is valid, but if the user was deleted / disabled / banned, the route still needs to reject them.

I think auth tests are where beginner FastAPI projects start becoming real backend projects.

What auth edge case do you think gets missed the most?

A lot of beginner FastAPI projects stop at:

u/app.post("/login")
def login():
    ...

But in real apps, “it works” is not the same as “it’s safe to ship.”

Some things I think every FastAPI route should be checked for:

• Does the route verify the current user owns the resource?
• Does it return only safe response fields?
• Are expired / invalid tokens tested?
• Are duplicate emails handled properly?
• Are async DB sessions used correctly?
• Are errors consistent and not leaking internals?
• Are tests covering failure cases, not only happy paths?

The biggest jump for me was realizing that backend quality is mostly about edge cases.

Curious what other FastAPI devs here check before shipping a route?

A lot of beginner FastAPI projects stop at:

u/app.post("/login")
def login():
    ...

But in real apps, “it works” is not the same as “it’s safe to ship.”

Some things I think every FastAPI route should be checked for:

• Does the route verify the current user owns the resource?
• Does it return only safe response fields?
• Are expired / invalid tokens tested?
• Are duplicate emails handled properly?
• Are async DB sessions used correctly?
• Are errors consistent and not leaking internals?
• Are tests covering failure cases, not only happy paths?

The biggest jump for me was realizing that backend quality is mostly about edge cases.

Curious what other FastAPI devs here check before shipping a route?