pytest "collected 0 items / 1 error" in CI

pytest tried to import a test module and that import raised, so it collected zero tests and reported a collection error. The real failure is the import error shown in the errors section, not a failing assertion.

What this error means

The summary reads collected 0 items / 1 error (or N items / 1 error), with an ERRORS section showing the import that failed. Because collection errored, the affected module contributed no tests.

pytest output

==================== ERRORS ====================
____________ ERROR collecting tests/test_api.py ____________
ImportError while importing test module 'tests/test_api.py'.
...
ModuleNotFoundError: No module named 'app.services'
=========== 0 items collected / 1 error ===========

Common causes

A test module fails to import

An import at the top of a test file (a missing dependency, a renamed module, or a first-party package not installed) raises during collection, so pytest cannot gather its tests.

A syntax or import-time error in the module

A SyntaxError or an exception raised at module import time prevents collection of that file entirely.

How to fix it

Fix the import shown in the errors section

Read the ERROR collecting ... block - it names the file and the import that failed.
Install the missing dependency, or pip install -e . so first-party imports resolve.
Re-run; once the import succeeds, the module’s tests are collected.

Reproduce the import directly

Importing the test module in isolation surfaces the same error faster.

Terminal

python -c "import tests.test_api"
pip install -e .   # if it is a first-party import

How to prevent it

Install the project (pip install -e .) so test imports resolve in CI.
Keep test dependencies declared and installed alongside the app.
Run a quick import smoke check before the full suite.