Profiles / #9
Passed Run of Nov 7, 17:55
Some tests got too few samples to explain their time.
Rerun with
pytest --flakytest-profile --flakytest-rate 2000.
Wall time
39.77 s
4 workers
Test time
1m 36s
sum of test durations
Tests
310
310 passed
Profiler
tachyon
1000 Hz ·
94,964 samples · Python 3.15.2 · flakytest 2026.0b1
Peak memory
657 MB
4 workers together
Where the time goes
Test time by category- Password hashing27.38 s
- Migrations25.36 s
- Libraries19.22 s
- Database13.37 s
- Templates2.97 s
- DB schema2.79 s
- Mocking1.80 s
- Imports1.57 s
- pytest404 ms
- Factories395 ms
- Unsampled328 ms
- App code102 ms
- Cache81 ms
- Deep copies57 ms
- Waiting23 ms
- Test code22 ms
- Network16 ms
- Logging16 ms
- Serialization13 ms
- Fixture loading1 ms
Session timeline
Other
7 ms
Tests
1m 36s
Startup
9.61 s
Collection
2.91 s
Test phases
Setup 28.46 s
Call 1m 07s
Teardown 848 ms
Fix next
Ranked by the time each fix saves per run
1
Use plain static file storage in tests
Static file storage/manifest handling costs 28.1s.
High
App code
28.14 s
per run
Fix: In test settings use STORAGES["staticfiles"] = {"BACKEND": "django.contrib.staticfiles.storage.StaticFilesStorage"} so templates don't need a manifest.
Read the guide
Details
Where:
- accounts/views.py:425 index · 909 ms
- starter_packs/tests.py:781 TestShareStarterPack.test_order_by · 749 ms
- starter_packs/views.py:862 share_starter_pack · 685 ms
- accounts/tests.py:550 TestAccountIndexRobots.assert_noindex · 601 ms
- accounts/tests.py:555 TestAccountIndexRobots.assert_indexable · 556 ms
- starter_packs/views.py:856 share_starter_pack · 544 ms
- confs/views.py:509 create_conference · 443 ms
- starter_packs/tests.py:841 TestShareStarterPack.test_api_formats · 429 ms
- starter_packs/tests.py:954 TestShareStarterPack._get_activitypub · 421 ms
- starter_packs/tests.py:1291 TestRemoteFollowStarterPack.test_deleted_pack_404 · 398 ms
Most affected tests:
- starter_packs/tests.py::TestFollowStarterPack::test_instance_unreachable
- starter_packs/tests.py::TestRemoteFollowStarterPack::test_deleted_pack_404
- confs/tests.py::TestMigratedLegacyConferences::test_djangoconafrica_page
- starter_packs/tests.py::TestStarterPacks::test_index_page
- accounts/tests.py::TestSelectedInstance::test_invalid_selected_instance
- confs/tests.py::TestCreateConference::test_rejects_more_than_three_icons
- accounts/tests.py::TestAccountIndexRobots::test_two_facets_are_noindex
- starter_packs/tests.py::TestShareStarterPack::test_api_activitypub_leaves_out_accounts_without_activitypub_id
2
Use a fast password hasher in tests
27.4s (29% of test time) is spent hashing passwords. Slow hashing protects real passwords; in tests it only burns CPU.
High
Password hashing
26.01 s
per run
Fix: In your test settings set PASSWORD_HASHERS = ["django.contrib.auth.hashers.MD5PasswordHasher"] (currently PBKDF2PasswordHasher).
Read the guide
Details
Only change the hasher in test settings. Tests that assert on a specific hash format need updating.
Where:
- confs/tests.py:1044 TestCreateConference.setUp · 5.21 s
- confs/tests.py:1176 TestEditConference.setUp · 3.81 s
- confs/tests.py:1177 TestEditConference.setUp · 3.73 s
- confs/tests.py:1175 TestEditConference.setUp · 3.68 s
- confs/tests.py:1371 TestApproveConference.setUp · 2.82 s
- confs/tests.py:1372 TestApproveConference.setUp · 2.73 s
- confs/tests.py:1317 TestConferenceApprovalVisibility.setUp · 1.54 s
- confs/tests.py:1316 TestConferenceApprovalVisibility.setUp · 1.53 s
- fedidevs/tests.py:63 TestAnonymousCacheAndCsrf.test_authenticated_html_is_private_and_keeps_csrf_header · 660 ms
- confs/tests.py:1295 TestUnapproveConference.setUp · 607 ms
Most affected tests:
- confs/tests.py::TestEditConference::test_other_user_forbidden_on_approved_conference
- confs/tests.py::TestEditConference::test_other_user_forbidden
- confs/tests.py::TestEditConference::test_owner_can_edit
- confs/tests.py::TestEditConference::test_edit_does_not_change_slug
- confs/tests.py::TestEditConference::test_owner_can_edit_after_approval
- confs/tests.py::TestApproveConference::test_non_staff_forbidden
- fedidevs/tests.py::TestAnonymousCacheAndCsrf::test_authenticated_html_is_private_and_keeps_csrf_header
- confs/tests.py::TestApproveConference::test_get_not_allowed
3
Stop re-running migrations on every test run
Migrations take 25.4s per run, before the first test can start.
High
Migrations
22.82 s
per run
Fix: Run with --reuse-db (add it to addopts in pytest.ini/pyproject) so the test database survives between runs; pass --create-db when migrations change. If no test depends on data migrations, --nomigrations builds the schema straight from the models, which is faster still.
Read the guide
Details
CI should still build the database from scratch (no --reuse-db) so broken migrations are caught.
Where:
- confs/tests.py:432 TestLegacyConferenceDataMigration._migrate · 1.16 s
- confs/migrations/0031_seed_conference_tags.py:14 seed_conference_tags · 806 ms
- confs/migrations/0033_remove_legacy_conference_tables.py:388 _get_or_create_conference · 143 ms
- confs/tests.py:412 TestLegacyConferenceDataMigration._leaf_targets · 130 ms
- confs/tests.py:430 TestLegacyConferenceDataMigration._migrate · 83 ms
- confs/tests.py:431 TestLegacyConferenceDataMigration._migrate · 66 ms
- confs/migrations/0033_remove_legacy_conference_tables.py:214 _pk_batches · 65 ms
- confs/migrations/0033_remove_legacy_conference_tables.py:325 _refresh_account_counts · 50 ms
- confs/migrations/0033_remove_legacy_conference_tables.py:398 migrate_legacy_pair · 48 ms
- starter_packs/migrations/0004_starterpack_published_at.py:9 set_published_at · 46 ms
Most affected tests:
- confs/tests.py::TestMigratedLegacyConferences::test_fwd50_date_redirects
- accounts/tests.py::TestAccountIndexRobots::test_two_facets_are_noindex
- confs/tests.py::TestSyncAnnouncements::test_is_idempotent_and_refreshes_unposted_content
- accounts/tests.py::TestSelectedInstance::test_invalid_selected_instance
- confs/tests.py::TestLegacyConferenceDataMigration::test_copies_overlapping_legacy_rows_without_clobbering_existing_data
- confs/tests.py::TestLegacyConferenceDataMigration::test_drops_legacy_tables_when_uniques_are_mysql_style_indexes
4
Create shared test data in setUpTestData instead of setUp
setUp() runs before every test and takes 26.5s in total (password hashing 26.3s, db 186ms, library 9ms) in 7 classes: TestFollowStarterPack (3 tests), TestApproveConference (6 tests), TestPostAnnouncements (6 tests), TestCreateConference (10 tests).
High
Database
18.53 s
per run
Fix: Move object creation that tests only read from setUp() into `@classmethod def setUpTestData(cls)`: it runs once per class and each test still sees the original rows (TestCase rolls back to a savepoint).
Read the guide
Details
Since Django 3.2 attributes assigned in setUpTestData are deep-copied per test, so in-memory changes don't leak between tests. Keep objects a test modifies in the database (or re-fetches) as before.
Where:
- confs/tests.py:1044 TestCreateConference.setUp · 5.23 s
- confs/tests.py:1176 TestEditConference.setUp · 3.83 s
- confs/tests.py:1177 TestEditConference.setUp · 3.74 s
- confs/tests.py:1175 TestEditConference.setUp · 3.69 s
- confs/tests.py:1371 TestApproveConference.setUp · 2.84 s
- confs/tests.py:1372 TestApproveConference.setUp · 2.74 s
- confs/tests.py:1317 TestConferenceApprovalVisibility.setUp · 1.55 s
- confs/tests.py:1316 TestConferenceApprovalVisibility.setUp · 1.54 s
- confs/tests.py:1295 TestUnapproveConference.setUp · 610 ms
- confs/tests.py:1296 TestUnapproveConference.setUp · 601 ms
Most affected tests:
- confs/tests.py::TestEditConference::test_other_user_forbidden_on_approved_conference
- confs/tests.py::TestEditConference::test_other_user_forbidden
- confs/tests.py::TestEditConference::test_owner_can_edit
- confs/tests.py::TestEditConference::test_edit_does_not_change_slug
- confs/tests.py::TestEditConference::test_owner_can_edit_after_approval
- confs/tests.py::TestApproveConference::test_non_staff_forbidden
- confs/tests.py::TestApproveConference::test_get_not_allowed
- confs/tests.py::TestApproveConference::test_staff_approves
5
Disable django-debug-toolbar in tests
django-debug-toolbar is installed in the test settings and costs 11.0s.
High
App code
10.98 s
per run
Fix: Only add debug_toolbar to INSTALLED_APPS and MIDDLEWARE when not testing (e.g. `if DEBUG and not TESTING:`).
Read the guide
Details
Where:
- accounts/views.py:425 index · 909 ms
- starter_packs/views.py:862 share_starter_pack · 685 ms
- starter_packs/views.py:856 share_starter_pack · 544 ms
- confs/views.py:509 create_conference · 443 ms
- confs/views.py:296 _conference_detail · 355 ms
- starter_packs/views.py:185 starter_packs · 351 ms
- starter_packs/views.py:60 get_editable_pack · 297 ms
- accounts/views.py:28 CountlessPage.__init__ · 296 ms
- accounts/templatetags/account_extras.py:36 instances_datalist · 282 ms
- accounts/templatetags/account_extras.py:34 instances_datalist · 277 ms
Most affected tests:
- confs/tests.py::TestMigratedLegacyConferences::test_djangoconafrica_page
- accounts/tests.py::TestAccountIndexRobots::test_two_facets_are_noindex
- starter_packs/tests.py::TestStarterPacks::test_index_page
- accounts/tests.py::TestStaticPages::test_developers_on_mastodon
- confs/tests.py::TestCreateConference::test_form_renders_for_authenticated_user
- accounts/tests.py::TestSelectedInstance::test_invalid_selected_instance
- accounts/tests.py::TestAccountIndexRobots::test_single_facet_is_indexable
- fedidevs/tests.py::TestAnonymousCacheAndCsrf::test_anonymous_forms_work_after_csrf_bootstrap
6
Repeated queries (N+1) in the code under test
10 tests run the same query 10+ times, e.g. 45x in test_invalid_selected_instance. N+1 queries slow the tests and production alike.
High
Database
10.58 s
per run
Fix: Django: fetch related rows in one query with select_related() for foreign keys and prefetch_related() for reverse/many-to-many relations, then lock the count in with assertNumQueries (or pytest-django's django_assert_num_queries).
Read the guide
Details
This changes application code, so it speeds up production too; the tests stay as they are.
- 45x in test_invalid_selected_instance: SELECT "confs_conferencetag"."id", "confs_conferencetag"."name", "confs_conferencetag"."slug", "confs_conferencetag"."icon" FROM "confs_conferencetag" WHERE "confs_conferencetag"."slug" = %s LIMIT ? FOR UPDATE
- 45x in test_fwd50_date_redirects: SELECT "confs_conferencetag"."id", "confs_conferencetag"."name", "confs_conferencetag"."slug", "confs_conferencetag"."icon" FROM "confs_conferencetag" WHERE "confs_conferencetag"."slug" = %s LIMIT ? FOR UPDATE
- 45x in test_two_facets_are_noindex: SELECT "confs_conferencetag"."id", "confs_conferencetag"."name", "confs_conferencetag"."slug", "confs_conferencetag"."icon" FROM "confs_conferencetag" WHERE "confs_conferencetag"."slug" = %s LIMIT ? FOR UPDATE
- 45x in test_is_idempotent_and_refreshes_unposted_content: SELECT "confs_conferencetag"."id", "confs_conferencetag"."name", "confs_conferencetag"."slug", "confs_conferencetag"."icon" FROM "confs_conferencetag" WHERE "confs_conferencetag"."slug" = %s LIMIT ? FOR UPDATE
- 44x in test_posts_from_yesterday_are_updated: SELECT COUNT(*) AS "__count" FROM "accounts_accountlookup" WHERE UPPER("accounts_accountlookup"."language"::text) LIKE UPPER(%s)
Most affected tests:
- accounts/tests.py::TestSelectedInstance::test_invalid_selected_instance
- confs/tests.py::TestMigratedLegacyConferences::test_fwd50_date_redirects
- accounts/tests.py::TestAccountIndexRobots::test_two_facets_are_noindex
- confs/tests.py::TestSyncAnnouncements::test_is_idempotent_and_refreshes_unposted_content
- stats/tests.py::TestStats::test_posts_from_yesterday_are_updated
- stats/tests.py::TestStats::test_store_daily_stats
- stats/tests.py::TestStats::test_store_daily_stats_with_accounts
- accounts/tests.py::TestInstanceIndexingBridgy::test_follows_redirect_and_coerces_null_version
7
Make the test database server skip durability work
Tests spend 41.5s (43%) in the database. Test databases don't need to survive a crash, so the server can skip flushing to disk.
Medium
Database
8.30 s
per run
Fix: For a PostgreSQL test server (Docker/CI service) start it with -c fsync=off -c synchronous_commit=off -c full_page_writes=off, and put its data directory on tmpfs; for MySQL use --innodb-flush-log-at-trx-commit=0 --skip-log-bin. Never on a server with data you need.
Read the guide
Details
Only affects crash safety of the throwaway test server; query behaviour is identical.
Where:
- confs/tests.py:432 TestLegacyConferenceDataMigration._migrate · 1.16 s
- confs/migrations/0031_seed_conference_tags.py:14 seed_conference_tags · 806 ms
- starter_packs/tests.py:397 TestToggleStarterPackAccount.test_toggle_after_limit · 672 ms
- starter_packs/views.py:856 share_starter_pack · 543 ms
- starter_packs/views.py:862 share_starter_pack · 336 ms
- starter_packs/views.py:60 get_editable_pack · 297 ms
- accounts/views.py:28 CountlessPage.__init__ · 296 ms
- accounts/templatetags/account_extras.py:36 instances_datalist · 282 ms
- accounts/templatetags/account_extras.py:34 instances_datalist · 277 ms
- starter_packs/views.py:858 share_starter_pack · 254 ms
Most affected tests:
- accounts/tests.py::TestSelectedInstance::test_invalid_selected_instance
- confs/tests.py::TestMigratedLegacyConferences::test_fwd50_date_redirects
- accounts/tests.py::TestAccountIndexRobots::test_two_facets_are_noindex
- confs/tests.py::TestSyncAnnouncements::test_is_idempotent_and_refreshes_unposted_content
- confs/tests.py::TestLegacyConferenceDataMigration::test_copies_overlapping_legacy_rows_without_clobbering_existing_data
- confs/tests.py::TestLegacyConferenceDataMigration::test_drops_legacy_tables_when_uniques_are_mysql_style_indexes
- starter_packs/tests.py::TestToggleStarterPackAccount::test_toggle_after_limit
- accounts/tests.py::TestInstanceIndexingBridgy::test_follows_redirect_and_coerces_null_version
8
pytest-xdist workers finish at very different times
The busiest worker ran 31.9s of tests, the least busy 20.9s.
Medium
Parallelism
5.47 s
per run
Fix: Use --dist worksteal (pytest-xdist 3.2+) so idle workers take tests from busy ones; if you use --dist loadscope/loadfile, split the biggest classes or modules.
Read the guide
Details
9
pytest takes a long time before the first test runs
Startup takes 9.6s and collection 2.9s on every run, even when you only run one test.
Medium
Imports
5.01 s
per run
Fix: Set testpaths and norecursedirs (node_modules, .venv, build, docs) so pytest doesn't walk unrelated directories; move heavy imports out of module level in test files and conftest.py into fixtures; check `python -X importtime -m pytest --collect-only -q` for the slowest imports.
Read the guide
Details
- mastodon_auth/tests.py (1.1s)
- starter_packs/tests.py (335ms)
- accounts/tests.py (57ms)
- confs/tests.py (13ms)
- stats/tests.py (6ms)
- fedidevs/settings.py (2.7s)
- debug_toolbar/panels/sql/__init__.py (1.4s)
- starter_packs/admin.py (761ms)
10
Run migrations once, not once per worker
Each of the 4 pytest-xdist workers builds its own test database by running every migration: 25.9s in total, about 6.5s per worker. 19.5s of it repeats work another worker already did.
Medium
Migrations
19.46 s
per run
Fix: Migrate once and copy the database: let one worker build the test database and have the others create theirs from it as a template (on PostgreSQL, CREATE DATABASE ... TEMPLATE ..., which copies files instead of running migrations). Django's own test runner already does this with --parallel.
Read the guide
Details
Every copy is built by the same migrations, so a broken migration still fails the run.
- {'total': 25.948, 'builds': 4, 'workers': 4, 'per_build': 6.487}
Tests
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Memory
Busiest worker peaked at 219 MB; all 4 together at about 657 MB| Worker | Tests | Peak | Grew by |
|---|---|---|---|
| gw0 | 111 | 200 MB | 49 MB |
| gw1 | 70 | 219 MB | 42 MB |
| gw2 | 94 | 211 MB | 60 MB |
| gw3 | 35 | 192 MB | 47 MB |
Slowest fixtures
Exact setup time across the session| Fixture | Scope | Calls | Total |
|---|---|---|---|
| _django_setup_unittest | class | 79 | 25.98 s |
| django_db_setup | session | 4 | 25.95 s |
| _unittest_setUpClass_fixture_TestShareStarterPack | class | 3 | 233 ms |
| _unittest_setUpClass_fixture_TestSelectedInstance | class | 1 | 199 ms |
| _unittest_setUpClass_fixture_TestPinAccountInStarterPack | class | 3 | 179 ms |
| _unittest_setUpClass_fixture_TestFollowStarterPack | class | 2 | 112 ms |
| _unittest_setUpClass_fixture_TestOwnerManagement | class | 2 | 96 ms |
| _unittest_setUpClass_fixture_TestDeleteStarterPack | class | 2 | 88 ms |
| _unittest_setUpClass_fixture_TestWebfingerBackfill | class | 1 | 85 ms |
| _unittest_setUpClass_fixture_TestStarterPacks | class | 2 | 77 ms |
| _unittest_setUpClass_fixture_TestEditStarterPack | class | 2 | 71 ms |
| _unittest_setUpClass_fixture_TestRemoteFollowStarterPack | class | 2 | 69 ms |
| _unittest_setUpClass_fixture_TestAddAccountsSearch | class | 1 | 56 ms |
| _unittest_setUpClass_fixture_TestFollowBg | class | 1 | 51 ms |
| _unittest_setUpClass_fixture_TestConferencePage | class | 1 | 46 ms |