## TL;DR

The fixture is misnamed, defined in the wrong conftest, or shadowed. Check the name matches exactly, the conftest is at the right level, and no plugin fixture overrides it.

## Error

```text
E       fixture 'db_session' not found
>       available fixtures: cache, capfd, ...
```

## Steps

1. Compare the requested name with the definition character by character. Expected: typos found fast.
2. Check conftest.py placement: fixtures apply to their directory and below. Expected: the conftest covers the test file.
3. Check for shadowing: a local fixture or plugin with the same name wins. Expected: the winner identified.
4. Verify the fixture is decorated with `@pytest.fixture`. Expected: decoration present.
5. Re-run with `--fixtures` to list what pytest sees. Expected: your fixture appears.

## When to use

- `fixture 'x' not found` at collection.
- After moving test files between directories.

## When not to use

- The fixture exists but errors inside (different bug).
- Plugin fixtures missing (install the plugin).

## Tool compatibility

- pytest 7/8; conftest.py discovery rules.

## Variant phrasings

### pytest fixture not available

Same error; check scope and naming.

### fixture called directly (newer pytest)

Fixtures cannot be called directly; request them as arguments.

## Why it happens

Fixture discovery is directory-scoped and name-exact. Moves, renames, and typos break it silently until collection.

## Edge cases

- `conftest.py` in the rootdir applies everywhere; nested ones override.
- Fixture name clashes with test function arguments confuse the error.
- `--import-mode` changes conftest discovery; keep it consistent.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_xJ9LUm1XPs0Vt6XISyeu1g