Too many slow tests in 'fast' (default) test suite run

This problem is magnified on gh-30995 because the RISC-V cores aren't all that performant (~10x slower than my M1 Macbook), however there are a lot of tests that are failing our design rule - which isn't super crisply written down I believe - of tests having to be marked as slow if they exceed 0.5 sec (maybe we've used 1 sec. in the past, but not more than that), unless there's a good reason not to.

Here are the 40 slowest tests I observe right now on a default spin test on an M1 Macbook:

====================================================================== slowest 40 durations =======================================================================
4.23s setup    build-install/usr/lib/python3.14/site-packages/numpy/_core/tests/test_cython.py::test_is_timedelta64_object
4.02s setup    build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_array_from_pyobj.py::TestIntent::test_in_out
3.44s setup    build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_parameter.py::TestParameters::test_constant_array
3.42s setup    build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_data.py::TestDataWithCommentsF77::test_data_stmts
3.40s setup    build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_isoc.py::TestISOC::test_bindc_function
3.38s setup    build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_data.py::TestDataF77::test_data_stmts
3.38s setup    build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_character.py::TestMiscCharacter::test_gh6308
3.36s setup    build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_data.py::TestData::test_crackedlines
3.34s setup    build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_crackfortran.py::TestDimSpec::test_inv_array_size[n]
3.34s setup    build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_string.py::TestDocStringArguments::test_example
3.33s setup    build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_callback.py::TestF77CallbackPythonTLS::test_docstring
3.30s setup    build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_callback.py::TestGH25211::test_gh25211
3.30s setup    build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_kind.py::TestKind::test_int
3.29s setup    build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_f2cmap.py::TestF2Cmap::test_gh15095
3.28s setup    build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_crackfortran.py::TestCrackFortran::test_gh2848
3.28s setup    build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_callback.py::TestF77Callback::test_docstring
3.25s setup    build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_character.py::TestStringScalarArr::test_char
3.24s setup    build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_mixed.py::TestMixed::test_docstring
3.24s setup    build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_data.py::TestDataMultiplierF77::test_data_stmts
3.23s setup    build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_character.py::TestCharacter::test_input[c]
3.22s setup    build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_string.py::TestFixedString::test_intent_in
3.21s setup    build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_character.py::TestStringAssumedLength::test_gh24008
3.21s setup    build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_crackfortran.py::TestNoSpace::test_module
3.17s setup    build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_crackfortran.py::TestExternal::test_external_as_statement
3.17s setup    build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_common.py::TestCommonWithUse::test_common_gh19161
3.14s call     build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_f2py2e.py::test_latex_doc_gh30268
2.90s setup    build-install/usr/lib/python3.14/site-packages/numpy/_core/tests/test_limited_api.py::test_limited_api
2.77s call     build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_f2py2e.py::test_no_distutils_backend
2.76s call     build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_f2py2e.py::test_untitled_cli
2.42s call     build-install/usr/lib/python3.14/site-packages/numpy/testing/tests/test_utils.py::TestAssertNoGcCycles::test_asserts
2.38s call     build-install/usr/lib/python3.14/site-packages/numpy/tests/test_ctypeslib.py::TestAsArray::test_reference_cycles
2.33s call     build-install/usr/lib/python3.14/site-packages/numpy/testing/tests/test_utils.py::TestAssertNoGcCycles::test_passes
2.16s call     build-install/usr/lib/python3.14/site-packages/numpy/lib/tests/test_function_base.py::TestLeaks::test_frompyfunc_leaks[bound-20]
2.13s call     build-install/usr/lib/python3.14/site-packages/numpy/linalg/tests/test_regression.py::TestRegression::test_openblas_threading
2.10s call     build-install/usr/lib/python3.14/site-packages/numpy/lib/tests/test_io.py::test_load_refcount
2.00s setup    build-install/usr/lib/python3.14/site-packages/numpy/_core/tests/test_mem_policy.py::test_set_policy
1.94s call     build-install/usr/lib/python3.14/site-packages/numpy/lib/tests/test_function_base.py::TestLeaks::test_frompyfunc_leaks[unbound-0]
1.78s call     build-install/usr/lib/python3.14/site-packages/numpy/lib/tests/test_function_base.py::TestPercentile::test_percentile_gh_29003_Fraction
1.24s call     build-install/usr/lib/python3.14/site-packages/numpy/tests/test_public_api.py::test_all_modules_are_expected_2
0.87s call     build-install/usr/lib/python3.14/site-packages/numpy/_core/tests/test_multiarray.py::TestPickling::test_roundtrip

Almost all of these are compile tests or special-purpose tests like GC checks or pickling roundtrips. There is no good reason for most of these to not be marked as slow.

I'll open a PR.

One constraint is that we need some test coverage for cython and f2py in the default test suite, so it needs a couple of compile tests. Same for pickling and multi-threaded tests. That can be sparse coverage though; we have a lot of 'full' test coverage in CI (1-2 jobs per platform), and CI exists for a reason.

Keeping that constraint in mind and then applying slow markers relatively liberally, we can get to a result like this (timing on M5 Macbook, all tests about 0.15 sec.):

3.15s setup    build-install/usr/lib/python3.14/site-packages/numpy/_core/tests/test_cython.py::test_is_timedelta64_object
2.50s setup    build-install/usr/lib/python3.14/site-packages/numpy/_core/tests/test_limited_api.py::test_limited_api
1.42s setup    build-install/usr/lib/python3.14/site-packages/numpy/_core/tests/test_mem_policy.py::test_default_policy_singleton
0.76s call     build-install/usr/lib/python3.14/site-packages/numpy/_core/tests/test_limited_api.py::test_limited_api
0.55s call     build-install/usr/lib/python3.14/site-packages/numpy/_core/tests/test_multiarray.py::TestPickling::test_roundtrip
0.46s call     build-install/usr/lib/python3.14/site-packages/numpy/_core/tests/test_multiarray.py::TestArrayFinalize::test_lifetime_on_error
0.38s call     build-install/usr/lib/python3.14/site-packages/numpy/random/tests/test_regression.py::TestRegression::test_shuffle_of_array_of_objects
0.37s call     build-install/usr/lib/python3.14/site-packages/numpy/f2py/tests/test_crackfortran.py::TestNameArgsPatternBacktracking::test_nameargspattern_backtracking[@)@bind                         @(@]
0.36s call     build-install/usr/lib/python3.14/site-packages/numpy/_core/tests/test_ufunc.py::TestUfunc::test_identityless_reduction_huge_array
0.33s call     build-install/usr/lib/python3.14/site-packages/numpy/_core/tests/test_arrayprint.py::test_multithreaded_array_printing
0.32s call     build-install/usr/lib/python3.14/site-packages/numpy/random/tests/test_generator_mt19937_regressions.py::TestRegression::test_shuffle_of_array_of_objects
0.30s call     build-install/usr/lib/python3.14/site-packages/numpy/random/tests/test_regression.py::TestRegression::test_shuffle_of_array_of_different_length_strings
0.28s call     build-install/usr/lib/python3.14/site-packages/numpy/random/tests/test_generator_mt19937_regressions.py::TestRegression::test_shuffle_of_array_of_different_length_strings
0.26s call     build-install/usr/lib/python3.14/site-packages/numpy/_core/tests/test_mem_policy.py::test_owner_is_base
0.25s call     build-install/usr/lib/python3.14/site-packages/numpy/_core/tests/test_cython.py::test_is_timedelta64_object
0.23s call     build-install/usr/lib/python3.14/site-packages/numpy/_core/tests/test_mem_overlap.py::test_internal_overlap_fuzz
0.20s call     build-install/usr/lib/python3.14/site-packages/numpy/_core/tests/test_regression.py::TestRegression::test_leak_in_structured_dtype_comparison
0.19s call     build-install/usr/lib/python3.14/site-packages/numpy/random/tests/test_randomstate.py::test_integer_repeat[multinomial]
0.19s call     build-install/usr/lib/python3.14/site-packages/numpy/_core/tests/test_multiarray.py::TestUnicodeEncoding::test_round_trip
0.19s call     build-install/usr/lib/python3.14/site-packages/numpy/_core/tests/test_multiarray.py::TestAlignment::test_various_alignments
0.18s call     build-install/usr/lib/python3.14/site-packages/numpy/_core/tests/test_arrayprint.py::TestArray2String::test_any_text
0.18s call     build-install/usr/lib/python3.14/site-packages/numpy/_core/tests/test_numeric.py::TestClip::test_clip_property
0.18s call     build-install/usr/lib/python3.14/site-packages/numpy/_core/tests/test_multiarray.py::TestMethods::test_sort_degraded

Total test time for spin test is then ~45 sec. on M5, so should be about 1.5 minute on M1 and 2-3 minutes on x86-64.

+1 for making the fast tests fast.

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Too many slow tests in `'fast'` (default) test suite run #31419

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Too many slow tests in 'fast' (default) test suite run #31419

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rgommers commented on May 13, 2026

mattip commented on May 13, 2026

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Too many slow tests in `'fast'` (default) test suite run #31419