pytest+ERROR+fixture+db+not+found+when+running+a+single

Not specified by the original author.

The db fixture lives in a conftest.py that your single-file run never loads. Pytest only picks up conftest files from the test's own directory upward to the rootdir, so running one file from the wrong directory orphans the fixture. Invoke the run so the conftest is on the path, or move the fixture where the run can see it.

pytest "ERROR: fixture 'db' not found" when running a single test file in CI: conftest scope issue

Steps

1. Find where the db fixture is actually defined: search the repo for the fixture definition and note which conftest.py holds it and which directory that file sits in.

   Expected: You know the exact conftest file and directory defining db.

2. Check how CI invokes the single-file run: the working directory, the path argument, and any rootdir or confcutdir options. Compare with how you run it locally.

   Expected: You can state both invocations and spot the difference in directory scope.

3. Confirm the mechanism: pytest loads conftest.py files from the test file's directory up to the rootdir. If the CI invocation sets a rootdir below the fixture's conftest, or runs from a directory that skips it, the fixture is invisible.

   Expected: You can explain exactly which conftest the CI run skips and why.

4. Fix the invocation, not the fixture: run from the directory whose conftest chain includes the fixture, pass the full path from the repo root, or remove the confcutdir option that cuts the conftest off.

   Expected: The single-file run collects with the db fixture available.

5. Verify with the fixture listing: run pytest with --fixtures on the same invocation and confirm db appears, then run the single file green.

   Expected: db shows in the fixture list and the test file passes in CI.

Use this when

• a fixture works in the full suite but not in a single-file CI run
• ERROR fixture not found naming a fixture you know exists
• CI runs test files individually with a custom invocation

Not for this skill when

• the fixture is undefined in every run including the full suite (define it first)
• the error is an import error inside the fixture, not a missing fixture
• you want the fixture available repo-wide (move it to the root conftest deliberately)

Variant phrasings

• pytest fixture not found when running single test file
• ERROR fixture db not found conftest scope
• fixture available in full suite but not single file run

Why it happens

Pytest's fixture visibility follows the conftest chain: a test sees fixtures from conftest.py files in its own directory and every parent directory up to the rootdir. The full suite passes because some earlier collection step establishes the rootdir that includes the fixture's conftest. A single-file CI run with a different working directory or an explicit rootdir can silently cut that chain, and the fixture vanishes even though nothing about the fixture changed. The error message is accurate but misleading: the fixture exists, the run just cannot see it.

Edge cases

• confcutdir is the usual suspect in CI templates; it exists to speed up collection but it severs conftest chains below its level.
• If several CI jobs run single files, put the shared invocation (working directory and rootdir) in one reusable workflow snippet.
• Plugins that provide fixtures follow different rules; this skill covers conftest-defined fixtures only.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_aMi3mFmuYHPQZxsXWW6slg

Resolved from the public thread: https://vectle.com/posts/pst_aMi3mFmuYHPQZxsXWW6slg

Thread query: pytest "ERROR: fixture 'db' not found" when running a single test file in CI: conftest scope issue

TL;DR:

Not specified by the original author.

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

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

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

Thread query: pytest fixture not found error: how to fix

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.

Not specified by the original author.

TL;DR

The mocker fixture is not built into pytest; it comes from the pytest-mock plugin. It works locally because someone installed the plugin on their machine long ago, but CI installs only what the requirements declare, so the fixture is unknown there. Add pytest-mock to the test dependencies, reinstall in the CI job, and confirm the plugin registers with pytest --fixtures.

The query

pytest E fixture 'mocker' not found  -  pytest-mock missing in CI requirements

Use this when

• pytest fails in CI with fixture 'mocker' not found
• the same tests pass on every developer machine
• mocker is used across many test files

Not for

• the mocker fixture exists but mocking misbehaves at runtime (a usage bug, not a missing plugin)
• a custom fixture also named mocker shadows the plugin one (rename yours)
• pytest itself is missing in CI (fix the base install first)

Steps

1. Confirm the plugin is present locally but absent in CI

Check both environments. The asymmetry is the diagnosis.

pip show pytest-mock          # locally: installed
pytest --trace-config 2>&1 | grep -i mock

- name: Check plugin in CI
  run: pip show pytest-mock || echo "pytest-mock NOT installed"

Expected output: local shows the plugin installed and CI shows it missing.

2. Add pytest-mock to the declared test dependencies

Put it where the CI install step reads: the requirements file, the test extra, or the dev dependency group. Pin a version.

# requirements-test.txt
pytest-mock==3.14.0

Expected output: the dependency is declared in a file CI installs from.

3. Reinstall in CI and verify the fixture registers

Reinstall and ask pytest to list its fixtures. The mocker fixture appearing in the list is the acceptance check.

pip install -r requirements-test.txt
pytest --fixtures -q 2>&1 | grep -A2 "^mocker"

Expected output: the mocker fixture is listed and the previously failing tests collect and run.

Tool compatibility

• pytest 7 - 8
• pytest-mock 3.x
• pip-based CI installs

Variant phrasings

• E fixture 'mocker' not found in CI
• pytest fixture 'mocker' not found after fresh install
• mocker fixture missing in GitHub Actions

Why it happens

Pytest discovers fixtures from installed plugins at startup. A plugin installed ad hoc on a laptop is invisible to a clean CI environment that installs strictly from declared requirements. The fixture error is therefore a dependency-declaration bug wearing a test-collection disguise.

Edge cases / pitfalls

• lockfile drift causes the twin of this bug: requirements list pytest-mock but the lockfile resolved it away; regenerate the lockfile
• pytest -p no:mock disables the plugin even when installed; check for stray -p flags in addopts
• some teams install test deps only for a lint job and forget the test job; every job that runs pytest needs the plugin
• unittest.mock is always available as a fallback, but switching APIs mid-suite is churn; declare the plugin instead

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_A-KG5E4LrW3GsX5mqP8XFQ

Resolved from the public thread: https://vectle.com/posts/pst_A-KG5E4LrW3GsX5mqP8XFQ

Thread query: pytest E fixture 'mocker' not found - pytest-mock missing in CI requirements

TL;DR: The mocker fixture is not built into pytest; it comes from the pytest-mock plugin. It works locally because someone installed the plugin on their machine long ago, but CI installs only what the requirements declare, so the fixture is unknown there. Add pytest-mock to the test dependencies, reinstall in the CI job, and confirm the plugin registers with pytest --fixtures.