Profiles / #10
Passed Run of Nov 7, 23:52
Some tests got too few samples to explain their time.
Rerun with
pytest --flakytest-profile --flakytest-rate 2000.
Wall time
24.60 s
4 workers
Test time
54.75 s
sum of test durations
Tests
310
310 passed
Profiler
tachyon
1000 Hz ·
53,211 samples · Python 3.15.2 · flakytest 2026.0b1
Peak memory
652 MB
4 workers together
Where the time goes
Test time by category- Password hashing16.28 s
- Migrations14.16 s
- Libraries9.31 s
- Database8.49 s
- DB schema2.79 s
- Imports1.01 s
- Templates979 ms
- Mocking855 ms
- pytest264 ms
- Unsampled250 ms
- Factories188 ms
- App code65 ms
- Deep copies41 ms
- Cache13 ms
- Waiting12 ms
- Test code12 ms
- Network11 ms
- Logging10 ms
- Serialization5 ms
- Fixture loading2 ms
Session timeline
Other
2 ms
Tests
54.94 s
Startup
4.98 s
Collection
1.53 s
Test phases
Setup 16.51 s
Call 37.09 s
Teardown 1.15 s
Fix next
Ranked by the time each fix saves per run
1
Use a fast password hasher in tests
16.3s (30% of test time) is spent hashing passwords. Slow hashing protects real passwords; in tests it only burns CPU.
High
Password hashing
15.47 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 · 2.91 s
- confs/tests.py:1176 TestEditConference.setUp · 2.25 s
- confs/tests.py:1177 TestEditConference.setUp · 2.23 s
- confs/tests.py:1175 TestEditConference.setUp · 2.18 s
- confs/tests.py:1371 TestApproveConference.setUp · 1.65 s
- confs/tests.py:1372 TestApproveConference.setUp · 1.63 s
- confs/tests.py:1316 TestConferenceApprovalVisibility.setUp · 1.03 s
- confs/tests.py:1317 TestConferenceApprovalVisibility.setUp · 1.03 s
- confs/tests.py:1296 TestUnapproveConference.setUp · 403 ms
- confs/tests.py:1295 TestUnapproveConference.setUp · 401 ms
Most affected tests:
- confs/tests.py::TestEditConference::test_edit_does_not_change_slug
- 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_owner_can_edit_after_approval
- confs/tests.py::TestApproveConference::test_staff_approves
- confs/tests.py::TestEditConference::test_owner_can_view_edit_form
- confs/tests.py::TestApproveConference::test_non_staff_forbidden
2
Use plain static file storage in tests
Static file storage/manifest handling costs 13.7s.
High
App code
13.73 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:
- starter_packs/views.py:862 share_starter_pack · 413 ms
- accounts/views.py:425 index · 397 ms
- starter_packs/tests.py:736 TestShareStarterPack.test_non_discoverable_accounts · 324 ms
- confs/tests.py:875 TestConferencePage.test_conference_with_utc_with_date_no_posts · 276 ms
- starter_packs/tests.py:125 TestCreateStarterPack.test_form_error · 264 ms
- accounts/tests.py:536 TestStaticPages.test_developers_on_mastodon · 254 ms
- starter_packs/tests.py:1068 TestPinAccountInStarterPack.test_pin_limit · 251 ms
- confs/tests.py:1153 TestCreateConference.test_rejects_more_than_three_icons · 249 ms
- starter_packs/tests.py:841 TestShareStarterPack.test_api_formats · 225 ms
- confs/tests.py:193 TestMigratedLegacyConferences.test_djangoconus_date_redirects · 221 ms
Most affected tests:
- starter_packs/tests.py::TestShareStarterPack::test_non_discoverable_accounts
- confs/tests.py::TestConferencePage::test_conference_with_utc_with_date_no_posts
- starter_packs/tests.py::TestCreateStarterPack::test_form_error
- accounts/tests.py::TestStaticPages::test_developers_on_mastodon
- starter_packs/tests.py::TestPinAccountInStarterPack::test_pin_limit
- confs/tests.py::TestCreateConference::test_rejects_more_than_three_icons
- starter_packs/tests.py::TestEditStarterPackAccounts::test_not_owned_starter_pack
- confs/tests.py::TestMigratedLegacyConferences::test_djangoconus_date_redirects
3
Stop re-running migrations on every test run
Migrations take 14.2s per run, before the first test can start.
High
Migrations
12.75 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 · 640 ms
- confs/migrations/0031_seed_conference_tags.py:14 seed_conference_tags · 355 ms
- confs/migrations/0033_remove_legacy_conference_tables.py:388 _get_or_create_conference · 103 ms
- confs/tests.py:412 TestLegacyConferenceDataMigration._leaf_targets · 78 ms
- confs/migrations/0033_remove_legacy_conference_tables.py:214 _pk_batches · 48 ms
- confs/tests.py:430 TestLegacyConferenceDataMigration._migrate · 43 ms
- confs/tests.py:431 TestLegacyConferenceDataMigration._migrate · 33 ms
- confs/migrations/0033_remove_legacy_conference_tables.py:398 migrate_legacy_pair · 29 ms
- confs/migrations/0033_remove_legacy_conference_tables.py:325 _refresh_account_counts · 27 ms
- confs/migrations/0033_remove_legacy_conference_tables.py:368 _attach_lookups_and_tags · 21 ms
Most affected tests:
- accounts/tests.py::TestSelectedInstance::test_invalid_selected_instance
- confs/tests.py::TestSyncAnnouncements::test_is_idempotent_and_refreshes_unposted_content
- accounts/tests.py::TestAccountIndexRobots::test_two_facets_are_noindex
- confs/tests.py::TestMigratedLegacyConferences::test_fwd50_date_redirects
- 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 15.9s in total (password hashing 15.7s, db 159ms, factories 6ms) in 7 classes: TestApproveConference (6 tests), TestFollowStarterPack (3 tests), TestPostAnnouncements (6 tests), TestCreateConference (10 tests).
High
Database
11.12 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 · 2.92 s
- confs/tests.py:1176 TestEditConference.setUp · 2.26 s
- confs/tests.py:1177 TestEditConference.setUp · 2.25 s
- confs/tests.py:1175 TestEditConference.setUp · 2.19 s
- confs/tests.py:1371 TestApproveConference.setUp · 1.66 s
- confs/tests.py:1372 TestApproveConference.setUp · 1.64 s
- confs/tests.py:1316 TestConferenceApprovalVisibility.setUp · 1.03 s
- confs/tests.py:1317 TestConferenceApprovalVisibility.setUp · 1.03 s
- confs/tests.py:1296 TestUnapproveConference.setUp · 405 ms
- confs/tests.py:1295 TestUnapproveConference.setUp · 404 ms
Most affected tests:
- confs/tests.py::TestEditConference::test_edit_does_not_change_slug
- 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_owner_can_edit_after_approval
- confs/tests.py::TestApproveConference::test_staff_approves
- confs/tests.py::TestEditConference::test_owner_can_view_edit_form
- confs/tests.py::TestApproveConference::test_non_staff_forbidden
5
Repeated queries (N+1) in the code under test
10 tests run the same query 10+ times, e.g. 45x in test_fwd50_date_redirects. N+1 queries slow the tests and production alike.
High
Database
6.70 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_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_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_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:
- confs/tests.py::TestMigratedLegacyConferences::test_fwd50_date_redirects
- accounts/tests.py::TestSelectedInstance::test_invalid_selected_instance
- 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
6
Disable django-debug-toolbar in tests
django-debug-toolbar is installed in the test settings and costs 5.6s.
High
App code
5.62 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:
- starter_packs/views.py:862 share_starter_pack · 413 ms
- accounts/views.py:425 index · 397 ms
- accounts/tests.py:536 TestStaticPages.test_developers_on_mastodon · 240 ms
- accounts/views.py:28 CountlessPage.__init__ · 218 ms
- starter_packs/views.py:185 starter_packs · 209 ms
- starter_packs/views.py:60 get_editable_pack · 164 ms
- accounts/views.py:295 index · 142 ms
- accounts/templatetags/account_extras.py:36 instances_datalist · 121 ms
- confs/views.py:509 create_conference · 114 ms
- starter_packs/splash_images.py:77 get_splash_image_accounts · 113 ms
Most affected tests:
- accounts/tests.py::TestStaticPages::test_developers_on_mastodon
- accounts/tests.py::TestAccountIndexRobots::test_two_facets_are_noindex
- accounts/tests.py::TestSelectedInstance::test_invalid_selected_instance
- confs/tests.py::TestCreateConference::test_form_renders_for_authenticated_user
- confs/tests.py::TestCreateConference::test_advanced_days_are_saved
- accounts/tests.py::TestAccountIndexRobots::test_single_facet_is_indexable
- fedidevs/tests.py::TestAnonymousCacheAndCsrf::test_anonymous_forms_work_after_csrf_bootstrap
- starter_packs/tests.py::TestStarterPacks::test_index_page
7
Make the test database server skip durability work
Tests spend 25.4s (46%) in the database. Test databases don't need to survive a crash, so the server can skip flushing to disk.
Medium
Database
5.09 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 · 640 ms
- starter_packs/tests.py:397 TestToggleStarterPackAccount.test_toggle_after_limit · 448 ms
- confs/migrations/0031_seed_conference_tags.py:14 seed_conference_tags · 355 ms
- starter_packs/views.py:862 share_starter_pack · 274 ms
- accounts/views.py:28 CountlessPage.__init__ · 218 ms
- starter_packs/views.py:60 get_editable_pack · 164 ms
- stats/models.py:20 store_daily_stats · 144 ms
- accounts/views.py:295 index · 142 ms
- stats/models.py:12 store_daily_stats · 136 ms
- accounts/templatetags/account_extras.py:36 instances_datalist · 121 ms
Most affected tests:
- accounts/tests.py::TestSelectedInstance::test_invalid_selected_instance
- confs/tests.py::TestSyncAnnouncements::test_is_idempotent_and_refreshes_unposted_content
- accounts/tests.py::TestAccountIndexRobots::test_two_facets_are_noindex
- confs/tests.py::TestMigratedLegacyConferences::test_fwd50_date_redirects
- 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
- mastodon_auth/tests.py::MastodonRatelimitHeaderTests::test_creates_session_with_hook_when_none_given
8
pytest-xdist workers finish at very different times
The busiest worker ran 19.0s of tests, the least busy 11.6s.
Medium
Parallelism
3.71 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 5.0s and collection 1.5s on every run, even when you only run one test.
Medium
Imports
2.60 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 (603ms)
- starter_packs/tests.py (221ms)
- accounts/tests.py (52ms)
- confs/tests.py (10ms)
- posts/tests.py (2ms)
- fedidevs/settings.py (970ms)
- debug_toolbar/panels/sql/__init__.py (793ms)
- starter_packs/admin.py (677ms)
10
Run migrations once, not once per worker
Each of the 4 pytest-xdist workers builds its own test database by running every migration: 15.1s in total, about 3.8s per worker. 11.3s of it repeats work another worker already did.
Medium
Migrations
11.30 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': 15.062, 'builds': 4, 'workers': 4, 'per_build': 3.765}
Tests
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Memory
Busiest worker peaked at 210 MB; all 4 together at about 652 MB| Worker | Tests | Peak | Grew by |
|---|---|---|---|
| gw0 | 76 | 210 MB | 43 MB |
| gw1 | 103 | 187 MB | 43 MB |
| gw2 | 96 | 205 MB | 60 MB |
| gw3 | 35 | 183 MB | 42 MB |
Slowest fixtures
Exact setup time across the session| Fixture | Scope | Calls | Total |
|---|---|---|---|
| _django_setup_unittest | class | 78 | 15.08 s |
| django_db_setup | session | 4 | 15.06 s |
| _unittest_setUpClass_fixture_TestShareStarterPack | class | 3 | 146 ms |
| _unittest_setUpClass_fixture_TestSelectedInstance | class | 1 | 91 ms |
| _unittest_setUpClass_fixture_TestFollowStarterPack | class | 2 | 82 ms |
| _unittest_setUpClass_fixture_TestPinAccountInStarterPack | class | 2 | 69 ms |
| _unittest_setUpClass_fixture_TestOwnerManagement | class | 2 | 65 ms |
| _unittest_setUpClass_fixture_TestWebfingerBackfill | class | 1 | 60 ms |
| _unittest_setUpClass_fixture_TestEditStarterPackAccounts | class | 2 | 49 ms |
| _unittest_setUpClass_fixture_TestFollowBg | class | 1 | 44 ms |
| _unittest_setUpClass_fixture_TestCreateStarterPack | class | 2 | 43 ms |
| _unittest_setUpClass_fixture_TestAddAccountsSearch | class | 1 | 40 ms |
| _unittest_setUpClass_fixture_TestStarterPacks | class | 1 | 34 ms |
| _unittest_setUpClass_fixture_TestConferencePage | class | 1 | 31 ms |
| _unittest_setUpClass_fixture_TestRemoteFollowStarterPack | class | 2 | 29 ms |