Profiles / #8
Passed Run of Oct 26, 23:43
Some tests got too few samples to explain their time.
Rerun with
pytest --flakytest-profile --flakytest-rate 5000.
Wall time
39.50 s
4 workers
Test time
1m 35s
sum of test durations
Tests
308
308 passed
Profiler
tachyon
1000 Hz ·
93,189 samples · Python 3.15.1 · flakytest 2026.0b1
Peak memory
662 MB
4 workers together
Where the time goes
Test time by category- Password hashing27.35 s
- Migrations25.35 s
- Libraries18.89 s
- Database12.57 s
- Templates3.37 s
- DB schema2.67 s
- Imports1.95 s
- Mocking1.36 s
- pytest525 ms
- Factories389 ms
- Unsampled361 ms
- App code109 ms
- Deep copies67 ms
- Cache46 ms
- Network43 ms
- Test code16 ms
- Waiting16 ms
- Logging15 ms
- Serialization12 ms
Session timeline
Other
3 ms
Tests
1m 35s
Startup
8.45 s
Collection
3.50 s
Test phases
Setup 28.08 s
Call 1m 06s
Teardown 795 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 28.3s.
High
App code
28.28 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 · 1.01 s
- starter_packs/tests.py:841 TestShareStarterPack.test_api_formats · 740 ms
- confs/views.py:509 create_conference · 691 ms
- accounts/tests.py:550 TestAccountIndexRobots.assert_noindex · 606 ms
- starter_packs/views.py:862 share_starter_pack · 528 ms
- starter_packs/tests.py:781 TestShareStarterPack.test_order_by · 419 ms
- starter_packs/tests.py:723 TestShareStarterPack.test_header_shows_gradient_and_account_avatars · 411 ms
- confs/tests.py:152 TestMigratedLegacyConferences._assert_no_naive_warning · 374 ms
- accounts/views.py:28 CountlessPage.__init__ · 335 ms
- confs/views.py:296 _conference_detail · 323 ms
Most affected tests:
- accounts/tests.py::TestAccountIndexRobots::test_two_facets_are_noindex
- starter_packs/tests.py::TestShareStarterPack::test_header_shows_gradient_and_account_avatars
- confs/tests.py::TestCreateConference::test_rejects_end_date_before_start
- accounts/tests.py::TestSelectedInstance::test_invalid_selected_instance
- confs/tests.py::TestCreateConference::test_form_renders_for_authenticated_user
- starter_packs/tests.py::TestShareStarterPack::test_order_by_5___alphabetical____4__3__2__1__0__
- confs/tests.py::TestMigratedLegacyConferences::test_djangoconafrica_page
- accounts/tests.py::TestAccountIndexRobots::test_single_facet_is_indexable
2
Use a fast password hasher in tests
27.3s (29% of test time) is spent hashing passwords. Slow hashing protects real passwords; in tests it only burns CPU.
High
Password hashing
25.98 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 · 5.51 s
- confs/tests.py:1177 TestEditConference.setUp · 3.78 s
- confs/tests.py:1175 TestEditConference.setUp · 3.75 s
- confs/tests.py:1176 TestEditConference.setUp · 3.37 s
- confs/tests.py:1371 TestApproveConference.setUp · 2.85 s
- confs/tests.py:1372 TestApproveConference.setUp · 2.80 s
- confs/tests.py:1317 TestConferenceApprovalVisibility.setUp · 1.52 s
- confs/tests.py:1316 TestConferenceApprovalVisibility.setUp · 1.51 s
- confs/tests.py:1295 TestUnapproveConference.setUp · 618 ms
- confs/tests.py:1296 TestUnapproveConference.setUp · 601 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::TestApproveConference::test_non_staff_forbidden
- confs/tests.py::TestApproveConference::test_staff_sees_approve_button_on_detail
- confs/tests.py::TestApproveConference::test_staff_approves
- confs/tests.py::TestEditConference::test_owner_can_edit_after_approval
3
Stop re-running migrations on every test run
Migrations take 25.3s per run, before the first test can start.
High
Migrations
22.81 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 · 1.33 s
- confs/migrations/0031_seed_conference_tags.py:14 seed_conference_tags · 761 ms
- confs/tests.py:412 TestLegacyConferenceDataMigration._leaf_targets · 148 ms
- confs/migrations/0033_remove_legacy_conference_tables.py:214 _pk_batches · 113 ms
- confs/migrations/0033_remove_legacy_conference_tables.py:388 _get_or_create_conference · 87 ms
- confs/tests.py:431 TestLegacyConferenceDataMigration._migrate · 71 ms
- starter_packs/migrations/0004_starterpack_published_at.py:9 set_published_at · 65 ms
- starter_packs/migrations/0009_starterpack_num_accounts.py:21 update_num_accounts · 61 ms
- confs/tests.py:486 TestLegacyConferenceDataMigration._seed_overlapping_legacy_data · 54 ms
- confs/migrations/0011_conferencepost_alter_conference_posts.py:13 update · 54 ms
Most affected tests:
- confs/tests.py::TestMigratedLegacyConferences::test_fwd50_date_redirects
- accounts/tests.py::TestAccountIndexRobots::test_two_facets_are_noindex
- accounts/tests.py::TestSelectedInstance::test_invalid_selected_instance
- 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
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 196ms, factories 12ms) in 7 classes: TestApproveConference (6 tests), TestFollowStarterPack (3 tests), TestCreateConference (10 tests), TestEditConference (9 tests).
High
Database
18.56 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 · 5.53 s
- confs/tests.py:1177 TestEditConference.setUp · 3.80 s
- confs/tests.py:1175 TestEditConference.setUp · 3.76 s
- confs/tests.py:1176 TestEditConference.setUp · 3.38 s
- confs/tests.py:1371 TestApproveConference.setUp · 2.86 s
- confs/tests.py:1372 TestApproveConference.setUp · 2.81 s
- confs/tests.py:1317 TestConferenceApprovalVisibility.setUp · 1.53 s
- confs/tests.py:1316 TestConferenceApprovalVisibility.setUp · 1.52 s
- confs/tests.py:1295 TestUnapproveConference.setUp · 620 ms
- confs/tests.py:1296 TestUnapproveConference.setUp · 603 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::TestApproveConference::test_non_staff_forbidden
- confs/tests.py::TestApproveConference::test_staff_sees_approve_button_on_detail
- confs/tests.py::TestApproveConference::test_staff_approves
- confs/tests.py::TestEditConference::test_owner_can_edit_after_approval
5
Disable django-debug-toolbar in tests
django-debug-toolbar is installed in the test settings and costs 11.8s.
High
App code
11.79 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 · 1.01 s
- confs/views.py:509 create_conference · 691 ms
- starter_packs/views.py:862 share_starter_pack · 528 ms
- accounts/views.py:28 CountlessPage.__init__ · 335 ms
- confs/views.py:296 _conference_detail · 323 ms
- starter_packs/views.py:60 get_editable_pack · 299 ms
- starter_packs/views.py:856 share_starter_pack · 285 ms
- starter_packs/views.py:858 share_starter_pack · 280 ms
- starter_packs/tests.py:192 TestEditStarterPack.test_not_logged_in · 267 ms
- starter_packs/views.py:729 share_starter_pack · 265 ms
Most affected tests:
- accounts/tests.py::TestAccountIndexRobots::test_two_facets_are_noindex
- confs/tests.py::TestCreateConference::test_rejects_end_date_before_start
- accounts/tests.py::TestSelectedInstance::test_invalid_selected_instance
- starter_packs/tests.py::TestShareStarterPack::test_order_by_5___alphabetical____4__3__2__1__0__
- starter_packs/tests.py::TestEditStarterPack::test_not_logged_in
- accounts/tests.py::TestAccountIndexRobots::test_single_facet_is_indexable
- confs/tests.py::TestCreateConference::test_form_renders_for_authenticated_user
- confs/tests.py::TestMigratedLegacyConferences::test_djangoconafrica_page
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
10.14 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_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
- 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
- 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
- confs/tests.py::TestSyncAnnouncements::test_is_idempotent_and_refreshes_unposted_content
- accounts/tests.py::TestAccountIndexRobots::test_two_facets_are_noindex
- 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
- confs/tests.py::TestLegacyConferenceDataMigration::test_copies_overlapping_legacy_rows_without_clobbering_existing_data
7
Make the test database server skip durability work
Tests spend 40.6s (43%) in the database. Test databases don't need to survive a crash, so the server can skip flushing to disk.
Medium
Database
8.12 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 · 1.33 s
- confs/migrations/0031_seed_conference_tags.py:14 seed_conference_tags · 761 ms
- starter_packs/tests.py:397 TestToggleStarterPackAccount.test_toggle_after_limit · 580 ms
- accounts/views.py:28 CountlessPage.__init__ · 335 ms
- starter_packs/views.py:60 get_editable_pack · 299 ms
- starter_packs/views.py:856 share_starter_pack · 285 ms
- starter_packs/views.py:858 share_starter_pack · 280 ms
- starter_packs/views.py:729 share_starter_pack · 265 ms
- stats/models.py:20 store_daily_stats · 252 ms
- starter_packs/views.py:862 share_starter_pack · 232 ms
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
- 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 20.3s.
Medium
Parallelism
5.83 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 8.5s and collection 3.5s on every run, even when you only run one test.
Medium
Imports
4.78 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 (1.5s)
- starter_packs/tests.py (338ms)
- accounts/tests.py (127ms)
- confs/tests.py (21ms)
- stats/tests.py (1ms)
- fedidevs/settings.py (2.1s)
- debug_toolbar/panels/sql/__init__.py (1.2s)
- starter_packs/admin.py (755ms)
10
Modules are imported while tests run
2.0s of test time is spent importing modules: whichever test imports a heavy module first pays for it, which makes that test look slow (and varies with test order).
Low
Imports
586 ms
per run
Fix: Find what is imported at the lines listed. Import heavy modules at the top of the test module or in conftest.py so the cost shows up once at collection, or avoid importing them in tests at all (e.g. stub the heavy dependency).
Read the guide
Details
Where:
- confs/views.py:366 <module> · 176 ms
- accounts/views.py:425 index · 120 ms
- confs/management/commands/syncannouncements.py:14 Command.handle · 107 ms
- accounts/tests.py:550 TestAccountIndexRobots.assert_noindex · 82 ms
- accounts/management/commands/indexer.py:81 Command.handle · 74 ms
- fedidevs/views.py:11 <module> · 69 ms
- mastodon_auth/forms.py:27 MastodonLoginForm.clean_instance · 50 ms
- confs/views.py:296 _conference_detail · 44 ms
- confs/views.py:509 create_conference · 41 ms
- confs/og_images.py:246 render_conference_og_image · 39 ms
Most affected tests:
- accounts/tests.py::TestAccountIndexRobots::test_two_facets_are_noindex
- accounts/tests.py::TestSelectedInstance::test_invalid_selected_instance
- confs/tests.py::TestSyncAnnouncements::test_is_idempotent_and_refreshes_unposted_content
- confs/tests.py::TestMigratedLegacyConferences::test_fwd50_date_redirects
- confs/tests.py::TestConferenceOgImage::test_management_command_renders_missing_and_skips_current
- mastodon_auth/tests.py::MastodonLoginFormTests::test_cleans_instance_to_ascii_hostname
- confs/tests.py::TestMigratedLegacyConferences::test_fwd50_page
- confs/tests.py::TestCreateConference::test_form_renders_for_authenticated_user
11
Run migrations once, not once per worker
Each of the 4 pytest-xdist workers builds its own test database by running every migration: 25.8s in total, about 6.5s per worker. 19.4s of it repeats work another worker already did.
Medium
Migrations
19.35 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': 25.805, 'builds': 4, 'workers': 4, 'per_build': 6.451}
Tests
201–308 of 308, slowest first · click a column to sort this page
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Memory
Busiest worker peaked at 209 MB; all 4 together at about 662 MB| Worker | Tests | Peak | Grew by |
|---|---|---|---|
| gw0 | 85 | 189 MB | 46 MB |
| gw1 | 71 | 209 MB | 43 MB |
| gw2 | 35 | 183 MB | 42 MB |
| gw3 | 117 | 204 MB | 60 MB |
Slowest fixtures
Exact setup time across the session| Fixture | Scope | Calls | Total |
|---|---|---|---|
| _django_setup_unittest | class | 76 | 25.84 s |
| django_db_setup | session | 4 | 25.81 s |
| _unittest_setUpClass_fixture_TestSelectedInstance | class | 1 | 213 ms |
| _unittest_setUpClass_fixture_TestShareStarterPack | class | 3 | 209 ms |
| _unittest_setUpClass_fixture_TestStarterPacks | class | 2 | 99 ms |
| _unittest_setUpClass_fixture_TestFollowStarterPack | class | 2 | 94 ms |
| _unittest_setUpClass_fixture_TestOwnerManagement | class | 2 | 88 ms |
| _unittest_setUpClass_fixture_TestPinAccountInStarterPack | class | 2 | 85 ms |
| _unittest_setUpClass_fixture_TestEditStarterPackAccounts | class | 2 | 76 ms |
| _unittest_setUpClass_fixture_TestWebfingerBackfill | class | 1 | 72 ms |
| _unittest_setUpClass_fixture_TestFollowBg | class | 1 | 70 ms |
| _unittest_setUpClass_fixture_TestRemoteFollowStarterPack | class | 2 | 46 ms |
| _unittest_setUpClass_fixture_TestAddAccountsSearch | class | 1 | 42 ms |
| _unittest_setUpClass_fixture_TestConferenceOgImage | class | 1 | 35 ms |
| _unittest_setUpClass_fixture_TestToggleStarterPackAccount | class | 1 | 35 ms |