pytest-collect-profile

Find what makes pytest collection slow.

pytest-collect-profile shows which collector operations take the most time and how long collection takes overall. It measures pytest directly, including custom collectors, so the report matches the suite pytest actually sees.

Installation

python -m pip install pytest-collect-profile

Quick start

Profile collection only — recommended

pytest --collect-profile-only

Start here when you want a diagnosis, not a test run. Pytest collects and selects the tests, the plugin prints one report, and the run stops. It does not print the usual list of collected nodes.

Only the 10 slowest collector operations are shown. The output stays useful in a terminal, a CI log, or coding-agent context even for large suites.

Profile collection, then run tests

pytest --collect-profile

Use this when you want to see the profile without changing your normal test run. The selected tests execute after the report is printed.

Need pytest's complete collected-node listing? Add --collect-only or --co to either command. An explicit pytest collect-only option keeps its native output.

Example report

====================== collect profile ======================
time      collector   node
1.421s    Module      tests/integration/test_api.py
0.612s    Class       tests/test_users.py::TestUsers
0.184s    Directory   tests/integration

Total collection: 2.340s | 842 items

Reading the report

• The slowest collector operations appear first, with at most 10 rows.
• Total collection measures the complete collection phase separately.
• Collector calls may be nested, so row times can overlap and are not meant to add up to the total.
• An empty root-session node ID is shown as <session>.

The report points to where collection time is spent. It does not guess why a collector is slow or promise that changing one row will reduce the total by the same amount.

Works with pytest

• The plugin is silent unless one of its two profiling options is present.
• Pytest continues to own selection, diagnostics, warnings, and exit status.
• -q, -qq, and -v keep their normal pytest meaning.
• Timings exist only for the current process. The plugin stores no history or cache and makes no network requests.

Compatibility

pytest-collect-profile requires Python 3.10 or newer and pytest 8.0 or newer. The project targets Linux, macOS, and Windows, with CI coverage across Python 3.10 through 3.14 and representative pytest 8.x and 9.x releases.

pytest-xdist

For a meaningful collection profile, run xdist projects serially:

pytest -n0 --collect-profile-only

The profile-only mode rejects active distributed execution and points to -n0. The regular --collect-profile mode does not aggregate worker results, so -n0 is recommended there as well.

Focused by design

pytest-collect-profile does one thing: profile collection. It does not profile test execution, fixtures, functions, or call stacks. It does not provide exports, history, run-to-run comparisons, thresholds, or configurable rankings and filters.

See the contribution guide for contribution guidance. This project is available under the terms of the MIT License.