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1# This file is part of Hypothesis, which may be found at
2# https://github.com/HypothesisWorks/hypothesis/
3#
4# Copyright the Hypothesis Authors.
5# Individual contributors are listed in AUTHORS.rst and the git log.
6#
7# This Source Code Form is subject to the terms of the Mozilla Public License,
8# v. 2.0. If a copy of the MPL was not distributed with this file, You can
9# obtain one at https://mozilla.org/MPL/2.0/.
11"""This module provides the core primitives of Hypothesis, such as given."""
13import base64
14import contextlib
15import dataclasses
16import datetime
17import inspect
18import io
19import math
20import os
21import sys
22import threading
23import time
24import traceback
25import types
26import unittest
27import warnings
28import zlib
29from collections import defaultdict
30from collections.abc import Callable, Coroutine, Generator, Hashable, Iterable, Sequence
31from dataclasses import dataclass, field
32from functools import partial
33from inspect import Parameter
34from random import Random
35from threading import Lock
36from types import EllipsisType
37from typing import (
38 Any,
39 BinaryIO,
40 TypeVar,
41 overload,
42)
43from unittest import TestCase
45from hypothesis import strategies as st
46from hypothesis._settings import (
47 HealthCheck,
48 Phase,
49 Verbosity,
50 all_settings,
51 local_settings,
52 settings as Settings,
53)
54from hypothesis.control import BuildContext, currently_in_test_context
55from hypothesis.database import choices_from_bytes, choices_to_bytes
56from hypothesis.errors import (
57 BackendCannotProceed,
58 DeadlineExceeded,
59 DidNotReproduce,
60 FailedHealthCheck,
61 FlakyFailure,
62 FlakyReplay,
63 Found,
64 Frozen,
65 HypothesisException,
66 HypothesisWarning,
67 InvalidArgument,
68 NoSuchExample,
69 StopTest,
70 Unsatisfiable,
71 UnsatisfiedAssumption,
72)
73from hypothesis.internal import observability
74from hypothesis.internal.compat import (
75 PYPY,
76 BaseExceptionGroup,
77 add_note,
78 bad_django_TestCase,
79 get_type_hints,
80 int_from_bytes,
81)
82from hypothesis.internal.conjecture.choice import ChoiceT
83from hypothesis.internal.conjecture.data import ConjectureData, Status
84from hypothesis.internal.conjecture.engine import (
85 BUFFER_SIZE,
86 ConjectureRunner,
87 ExitReason,
88)
89from hypothesis.internal.conjecture.junkdrawer import (
90 ensure_free_stackframes,
91 gc_cumulative_time,
92)
93from hypothesis.internal.conjecture.providers import (
94 BytestringProvider,
95 PrimitiveProvider,
96)
97from hypothesis.internal.conjecture.shrinker import sort_key
98from hypothesis.internal.entropy import deterministic_PRNG
99from hypothesis.internal.escalation import (
100 InterestingOrigin,
101 current_pytest_item,
102 format_exception,
103 get_trimmed_traceback,
104 is_hypothesis_file,
105)
106from hypothesis.internal.healthcheck import fail_health_check
107from hypothesis.internal.observability import (
108 InfoObservation,
109 InfoObservationType,
110 deliver_observation,
111 make_testcase,
112 observability_enabled,
113)
114from hypothesis.internal.reflection import (
115 convert_positional_arguments,
116 define_function_signature,
117 function_digest,
118 get_pretty_function_description,
119 get_signature,
120 impersonate,
121 is_mock,
122 nicerepr,
123 proxies,
124 repr_call,
125)
126from hypothesis.internal.scrutineer import (
127 MONITORING_TOOL_ID,
128 Trace,
129 Tracer,
130 explanatory_lines,
131 tractable_coverage_report,
132)
133from hypothesis.internal.validation import check_type
134from hypothesis.reporting import (
135 current_verbosity,
136 report,
137 verbose_report,
138 with_reporter,
139)
140from hypothesis.statistics import describe_statistics, describe_targets, note_statistics
141from hypothesis.strategies._internal.misc import NOTHING
142from hypothesis.strategies._internal.strategies import (
143 Ex,
144 SearchStrategy,
145 check_strategy,
146)
147from hypothesis.utils.conventions import not_set
148from hypothesis.utils.threading import ThreadLocal
149from hypothesis.vendor.pretty import RepresentationPrinter
150from hypothesis.version import __version__
152TestFunc = TypeVar("TestFunc", bound=Callable)
155running_under_pytest = False
156pytest_shows_exceptiongroups = True
157global_force_seed = None
158# this variable stores "engine-global" constants, which are global relative to a
159# ConjectureRunner instance (roughly speaking). Since only one conjecture runner
160# instance can be active per thread, making engine constants thread-local prevents
161# the ConjectureRunner instances of concurrent threads from treading on each other.
162threadlocal = ThreadLocal(_hypothesis_global_random=lambda: None)
165@dataclass(slots=True, frozen=False)
166class Example:
167 args: Any
168 kwargs: Any
169 # Plus two optional arguments for .xfail()
170 raises: Any = field(default=None)
171 reason: Any = field(default=None)
174@dataclass(slots=True, frozen=True)
175class ReportableError:
176 fragments: list[str]
177 exception: BaseException
180# TODO_DOCS link to not-yet-existent patch-dumping docs
183class example:
184 """
185 Add an explicit input to a Hypothesis test, which Hypothesis will always
186 try before generating random inputs. This combines the randomized nature of
187 Hypothesis generation with a traditional parametrized test.
189 For example:
191 .. code-block:: python
193 @example("Hello world")
194 @example("some string with special significance")
195 @given(st.text())
196 def test_strings(s):
197 pass
199 will call ``test_strings("Hello World")`` and
200 ``test_strings("some string with special significance")`` before generating
201 any random inputs. |@example| may be placed in any order relative to |@given|
202 and |@settings|.
204 |Explicit examples| from |@example| are run in the
205 |Phase.explicit| phase. Explicit examples do not count towards
206 |settings.max_examples|. Note that explicit examples added by |@example| do
207 not shrink. If an explicit example fails, Hypothesis will stop and report
208 the failure without generating any random inputs.
210 |@example| can also be used to easily reproduce a failure. For instance, if
211 Hypothesis reports that ``f(n=[0, math.nan])`` fails, you can add
212 ``@example(n=[0, math.nan])`` to your test to quickly reproduce that failure.
214 Arguments to ``@example``
215 -------------------------
217 Arguments to |@example| have the same behavior and restrictions as arguments
218 to |@given|. This means they may be either positional or keyword arguments
219 (but not both in the same |@example|):
221 .. code-block:: python
223 @example(1, 2)
224 @example(x=1, y=2)
225 @given(st.integers(), st.integers())
226 def test(x, y):
227 pass
229 Noting that while arguments to |@given| are strategies (like |st.integers|),
230 arguments to |@example| are values instead (like ``1``).
232 See the :ref:`given-arguments` section for full details.
233 """
235 def __init__(self, *args: Any, **kwargs: Any) -> None:
236 if args and kwargs:
237 raise InvalidArgument(
238 "Cannot mix positional and keyword arguments for examples"
239 )
240 if not (args or kwargs):
241 raise InvalidArgument("An example must provide at least one argument")
243 self.hypothesis_explicit_examples: list[Example] = []
244 self._this_example = Example(tuple(args), kwargs)
246 def __call__(self, test: TestFunc) -> TestFunc:
247 if not hasattr(test, "hypothesis_explicit_examples"):
248 test.hypothesis_explicit_examples = self.hypothesis_explicit_examples # type: ignore
249 test.hypothesis_explicit_examples.append(self._this_example) # type: ignore
250 return test
252 def xfail(
253 self,
254 condition: bool = True, # noqa: FBT002
255 *,
256 reason: str = "",
257 raises: type[BaseException] | tuple[type[BaseException], ...] = BaseException,
258 ) -> "example":
259 """Mark this example as an expected failure, similarly to
260 :obj:`pytest.mark.xfail(strict=True) <pytest.mark.xfail>`.
262 Expected-failing examples allow you to check that your test does fail on
263 some examples, and therefore build confidence that *passing* tests are
264 because your code is working, not because the test is missing something.
266 .. code-block:: python
268 @example(...).xfail()
269 @example(...).xfail(reason="Prices must be non-negative")
270 @example(...).xfail(raises=(KeyError, ValueError))
271 @example(...).xfail(sys.version_info[:2] >= (3, 12), reason="needs py 3.12")
272 @example(...).xfail(condition=sys.platform != "linux", raises=OSError)
273 def test(x):
274 pass
276 .. note::
278 Expected-failing examples are handled separately from those generated
279 by strategies, so you should usually ensure that there is no overlap.
281 .. code-block:: python
283 @example(x=1, y=0).xfail(raises=ZeroDivisionError)
284 @given(x=st.just(1), y=st.integers()) # Missing `.filter(bool)`!
285 def test_fraction(x, y):
286 # This test will try the explicit example and see it fail as
287 # expected, then go on to generate more examples from the
288 # strategy. If we happen to generate y=0, the test will fail
289 # because only the explicit example is treated as xfailing.
290 x / y
291 """
292 check_type(bool, condition, "condition")
293 check_type(str, reason, "reason")
294 if not (
295 isinstance(raises, type) and issubclass(raises, BaseException)
296 ) and not (
297 isinstance(raises, tuple)
298 and raises # () -> expected to fail with no error, which is impossible
299 and all(
300 isinstance(r, type) and issubclass(r, BaseException) for r in raises
301 )
302 ):
303 raise InvalidArgument(
304 f"{raises=} must be an exception type or tuple of exception types"
305 )
306 if condition:
307 self._this_example = dataclasses.replace(
308 self._this_example, raises=raises, reason=reason
309 )
310 return self
312 def via(self, whence: str, /) -> "example":
313 """Attach a machine-readable label noting what the origin of this example
314 was. |example.via| is completely optional and does not change runtime
315 behavior.
317 |example.via| is intended to support self-documenting behavior, as well as
318 tooling which might add (or remove) |@example| decorators automatically.
319 For example:
321 .. code-block:: python
323 # Annotating examples is optional and does not change runtime behavior
324 @example(...)
325 @example(...).via("regression test for issue #42")
326 @example(...).via("discovered failure")
327 def test(x):
328 pass
330 .. note::
332 `HypoFuzz <https://hypofuzz.com/>`_ uses |example.via| to tag examples
333 in the patch of its high-coverage set of explicit inputs, on
334 `the patches page <https://hypofuzz.com/example-dashboard/#/patches>`_.
335 """
336 if not isinstance(whence, str):
337 raise InvalidArgument(".via() must be passed a string")
338 # This is deliberately a no-op at runtime; the tools operate on source code.
339 return self
342def seed(seed: Hashable) -> Callable[[TestFunc], TestFunc]:
343 """
344 Seed the randomness for this test.
346 ``seed`` may be any hashable object. No exact meaning for ``seed`` is provided
347 other than that for a fixed seed value Hypothesis will produce the same
348 |test cases| (assuming that there are no other sources of nondeterminisim, such
349 as timing, hash randomization, or external state).
351 For example, the following test function and |RuleBasedStateMachine| will
352 each generate the same series of test cases each time they are executed:
354 .. code-block:: python
356 @seed(1234)
357 @given(st.integers())
358 def test(n): ...
360 @seed(6789)
361 class MyMachine(RuleBasedStateMachine): ...
363 If using pytest, you can alternatively pass ``--hypothesis-seed`` on the
364 command line.
366 Setting a seed overrides |settings.derandomize|, which is designed to enable
367 deterministic CI tests rather than reproducing observed failures.
369 Hypothesis will only print the seed which would reproduce a failure if a test
370 fails in an unexpected way, for instance inside Hypothesis internals.
371 """
373 def accept(test):
374 test._hypothesis_internal_use_seed = seed
375 current_settings = getattr(test, "_hypothesis_internal_use_settings", None)
376 test._hypothesis_internal_use_settings = Settings(
377 current_settings, database=None
378 )
379 return test
381 return accept
384# TODO_DOCS: link to /explanation/choice-sequence
387def reproduce_failure(version: str, blob: bytes) -> Callable[[TestFunc], TestFunc]:
388 """
389 Run the |test case| corresponding to the binary ``blob`` in order to reproduce a
390 failure. ``blob`` is a serialized version of the internal input representation
391 of Hypothesis.
393 A test decorated with |@reproduce_failure| always runs exactly one test case,
394 which is expected to cause a failure. If the provided ``blob`` does not
395 cause a failure, Hypothesis will raise |DidNotReproduce|.
397 Hypothesis will print an |@reproduce_failure| decorator if
398 |settings.print_blob| is ``True`` (which is the default in CI).
400 |@reproduce_failure| is intended to be temporarily added to your test suite in
401 order to reproduce a failure. It is not intended to be a permanent addition to
402 your test suite. Because of this, no compatibility guarantees are made across
403 Hypothesis versions, and |@reproduce_failure| will error if used on a different
404 Hypothesis version than it was created for.
406 .. seealso::
408 See also the :doc:`/tutorial/replaying-failures` tutorial.
409 """
411 def accept(test):
412 test._hypothesis_internal_use_reproduce_failure = (version, blob)
413 return test
415 return accept
418def reproduction_decorator(choices: Iterable[ChoiceT]) -> str:
419 return f"@reproduce_failure({__version__!r}, {encode_failure(choices)!r})"
422def encode_failure(choices: Iterable[ChoiceT]) -> bytes:
423 blob = choices_to_bytes(choices)
424 compressed = zlib.compress(blob)
425 if len(compressed) < len(blob):
426 blob = b"\1" + compressed
427 else:
428 blob = b"\0" + blob
429 return base64.b64encode(blob)
432def decode_failure(blob: bytes) -> Sequence[ChoiceT]:
433 try:
434 decoded = base64.b64decode(blob)
435 except Exception:
436 raise InvalidArgument(f"Invalid base64 encoded string: {blob!r}") from None
438 prefix = decoded[:1]
439 if prefix == b"\0":
440 decoded = decoded[1:]
441 elif prefix == b"\1":
442 try:
443 decoded = zlib.decompress(decoded[1:])
444 except zlib.error as err:
445 raise InvalidArgument(
446 f"Invalid zlib compression for blob {blob!r}"
447 ) from err
448 else:
449 raise InvalidArgument(
450 f"Could not decode blob {blob!r}: Invalid start byte {prefix!r}"
451 )
453 choices = choices_from_bytes(decoded)
454 if choices is None:
455 raise InvalidArgument(f"Invalid serialized choice sequence for blob {blob!r}")
457 return choices
460def _invalid(message, *, exc=InvalidArgument, test, given_kwargs):
461 @impersonate(test)
462 def wrapped_test(*arguments, **kwargs): # pragma: no cover # coverage limitation
463 raise exc(message)
465 wrapped_test.is_hypothesis_test = True
466 wrapped_test.hypothesis = HypothesisHandle(
467 inner_test=test,
468 _get_fuzz_target=wrapped_test,
469 _given_kwargs=given_kwargs,
470 )
471 return wrapped_test
474def is_invalid_test(test, original_sig, given_arguments, given_kwargs):
475 """Check the arguments to ``@given`` for basic usage constraints.
477 Most errors are not raised immediately; instead we return a dummy test
478 function that will raise the appropriate error if it is actually called.
479 When the user runs a subset of tests (e.g via ``pytest -k``), errors will
480 only be reported for tests that actually ran.
481 """
482 invalid = partial(_invalid, test=test, given_kwargs=given_kwargs)
484 if not (given_arguments or given_kwargs):
485 return invalid("given must be called with at least one argument")
487 params = list(original_sig.parameters.values())
488 pos_params = [p for p in params if p.kind is p.POSITIONAL_OR_KEYWORD]
489 kwonly_params = [p for p in params if p.kind is p.KEYWORD_ONLY]
490 if given_arguments and params != pos_params:
491 return invalid(
492 "positional arguments to @given are not supported with varargs, "
493 "varkeywords, positional-only, or keyword-only arguments"
494 )
496 if len(given_arguments) > len(pos_params):
497 return invalid(
498 f"Too many positional arguments for {test.__name__}() were passed to "
499 f"@given - expected at most {len(pos_params)} "
500 f"arguments, but got {len(given_arguments)} {given_arguments!r}"
501 )
503 if ... in given_arguments:
504 return invalid(
505 "... was passed as a positional argument to @given, but may only be "
506 "passed as a keyword argument or as the sole argument of @given"
507 )
509 if given_arguments and given_kwargs:
510 return invalid("cannot mix positional and keyword arguments to @given")
511 extra_kwargs = [
512 k for k in given_kwargs if k not in {p.name for p in pos_params + kwonly_params}
513 ]
514 if extra_kwargs and (params == [] or params[-1].kind is not params[-1].VAR_KEYWORD):
515 arg = extra_kwargs[0]
516 extra = ""
517 if arg in all_settings:
518 extra = f". Did you mean @settings({arg}={given_kwargs[arg]!r})?"
519 return invalid(
520 f"{test.__name__}() got an unexpected keyword argument {arg!r}, "
521 f"from `{arg}={given_kwargs[arg]!r}` in @given{extra}"
522 )
523 if any(p.default is not p.empty for p in params):
524 return invalid("Cannot apply @given to a function with defaults.")
526 # This case would raise Unsatisfiable *anyway*, but by detecting it here we can
527 # provide a much more helpful error message for people e.g. using the Ghostwriter.
528 empty = [
529 f"{s!r} (arg {idx})" for idx, s in enumerate(given_arguments) if s is NOTHING
530 ] + [f"{name}={s!r}" for name, s in given_kwargs.items() if s is NOTHING]
531 if empty:
532 strats = "strategies" if len(empty) > 1 else "strategy"
533 return invalid(
534 f"Cannot generate test cases from empty {strats}: " + ", ".join(empty),
535 exc=Unsatisfiable,
536 )
539def execute_explicit_examples(state, wrapped_test, arguments, kwargs, original_sig):
540 assert isinstance(state, StateForActualGivenExecution)
541 posargs = [
542 p.name
543 for p in original_sig.parameters.values()
544 if p.kind is p.POSITIONAL_OR_KEYWORD
545 ]
547 for example in reversed(getattr(wrapped_test, "hypothesis_explicit_examples", ())):
548 assert isinstance(example, Example)
549 # All of this validation is to check that @example() got "the same" arguments
550 # as @given, i.e. corresponding to the same parameters, even though they might
551 # be any mixture of positional and keyword arguments.
552 if example.args:
553 assert not example.kwargs
554 if any(
555 p.kind is p.POSITIONAL_ONLY for p in original_sig.parameters.values()
556 ):
557 raise InvalidArgument(
558 "Cannot pass positional arguments to @example() when decorating "
559 "a test function which has positional-only parameters."
560 )
561 if len(example.args) > len(posargs):
562 raise InvalidArgument(
563 "example has too many arguments for test. Expected at most "
564 f"{len(posargs)} but got {len(example.args)}"
565 )
566 example_kwargs = dict(
567 zip(posargs[-len(example.args) :], example.args, strict=True)
568 )
569 else:
570 example_kwargs = dict(example.kwargs)
571 given_kws = ", ".join(
572 repr(k) for k in sorted(wrapped_test.hypothesis._given_kwargs)
573 )
574 example_kws = ", ".join(repr(k) for k in sorted(example_kwargs))
575 if given_kws != example_kws:
576 raise InvalidArgument(
577 f"Inconsistent args: @given() got strategies for {given_kws}, "
578 f"but @example() got arguments for {example_kws}"
579 ) from None
581 # This is certainly true because the example_kwargs exactly match the params
582 # reserved by @given(), which are then remove from the function signature.
583 assert set(example_kwargs).isdisjoint(kwargs)
584 example_kwargs.update(kwargs)
586 if Phase.explicit not in state.settings.phases:
587 continue
589 with local_settings(state.settings):
590 fragments_reported = []
591 empty_data = ConjectureData.for_choices([])
592 try:
593 execute_example = partial(
594 state.execute_once,
595 empty_data,
596 is_final=True,
597 print_example=True,
598 example_kwargs=example_kwargs,
599 )
600 with with_reporter(fragments_reported.append):
601 if example.raises is None:
602 execute_example()
603 else:
604 # @example(...).xfail(...)
605 bits = ", ".join(nicerepr(x) for x in arguments) + ", ".join(
606 f"{k}={nicerepr(v)}" for k, v in example_kwargs.items()
607 )
608 try:
609 execute_example()
610 except failure_exceptions_to_catch() as err:
611 if not isinstance(err, example.raises):
612 raise
613 # Save a string form of this example; we'll warn if it's
614 # ever generated by the strategy (which can't be xfailed)
615 state.xfail_example_reprs.add(
616 repr_call(state.test, arguments, example_kwargs)
617 )
618 except example.raises as err:
619 # We'd usually check this as early as possible, but it's
620 # possible for failure_exceptions_to_catch() to grow when
621 # e.g. pytest is imported between import- and test-time.
622 raise InvalidArgument(
623 f"@example({bits}) raised an expected {err!r}, "
624 "but Hypothesis does not treat this as a test failure"
625 ) from err
626 else:
627 # Unexpectedly passing; always raise an error in this case.
628 reason = f" because {example.reason}" * bool(example.reason)
629 if example.raises is BaseException:
630 name = "exception" # special-case no raises= arg
631 elif not isinstance(example.raises, tuple):
632 name = example.raises.__name__
633 elif len(example.raises) == 1:
634 name = example.raises[0].__name__
635 else:
636 name = (
637 ", ".join(ex.__name__ for ex in example.raises[:-1])
638 + f", or {example.raises[-1].__name__}"
639 )
640 vowel = name.upper()[0] in "AEIOU"
641 raise AssertionError(
642 f"Expected a{'n' * vowel} {name} from @example({bits})"
643 f"{reason}, but no exception was raised."
644 )
645 except UnsatisfiedAssumption:
646 # Odd though it seems, we deliberately support explicit examples that
647 # are then rejected by a call to `assume()`. As well as iterative
648 # development, this is rather useful to replay Hypothesis' part of
649 # a saved failure when other arguments are supplied by e.g. pytest.
650 # See https://github.com/HypothesisWorks/hypothesis/issues/2125
651 with contextlib.suppress(StopTest):
652 empty_data.conclude_test(Status.INVALID)
653 except BaseException as err:
654 # In order to support reporting of multiple failing test cases, we yield
655 # each of the (report text, error) pairs we find back to the top-level
656 # runner. This also ensures that user-facing stack traces have as few
657 # frames of Hypothesis internals as possible.
658 err = err.with_traceback(get_trimmed_traceback())
660 # One user error - whether misunderstanding or typo - we've seen a few
661 # times is to pass strategies to @example() where values are expected.
662 # Checking is easy, and false-positives not much of a problem, so:
663 if isinstance(err, failure_exceptions_to_catch()) and any(
664 isinstance(arg, SearchStrategy)
665 for arg in example.args + tuple(example.kwargs.values())
666 ):
667 new = HypothesisWarning(
668 "The @example() decorator expects to be passed values, but "
669 "you passed strategies instead. See https://hypothesis."
670 "readthedocs.io/en/latest/reference/api.html#hypothesis"
671 ".example for details."
672 )
673 new.__cause__ = err
674 err = new
676 with contextlib.suppress(StopTest):
677 empty_data.conclude_test(Status.INVALID)
678 yield ReportableError(fragments_reported, err)
679 if (
680 state.settings.report_multiple_bugs
681 and pytest_shows_exceptiongroups
682 and isinstance(err, failure_exceptions_to_catch())
683 and not isinstance(err, skip_exceptions_to_reraise())
684 ):
685 continue
686 break
687 finally:
688 if fragments_reported:
689 assert fragments_reported[0].startswith("Failing test case")
690 fragments_reported[0] = fragments_reported[0].replace(
691 "Failing test case", "Failing explicit example", 1
692 )
694 empty_data.freeze()
695 if observability_enabled():
696 tc = make_testcase(
697 run_start=state._start_timestamp,
698 property=state.test_identifier,
699 data=empty_data,
700 how_generated="explicit example",
701 representation=state._string_repr,
702 timing=state._timing_features,
703 )
704 deliver_observation(tc)
706 if fragments_reported:
707 verbose_report(fragments_reported[0].replace("Failing", "Trying", 1))
708 for f in fragments_reported[1:]:
709 verbose_report(f)
712def get_random_for_wrapped_test(test, wrapped_test):
713 settings = wrapped_test._hypothesis_internal_use_settings
714 wrapped_test._hypothesis_internal_use_generated_seed = None
716 if wrapped_test._hypothesis_internal_use_seed is not None:
717 return Random(wrapped_test._hypothesis_internal_use_seed)
719 if settings.derandomize:
720 return Random(int_from_bytes(function_digest(test)))
722 if global_force_seed is not None:
723 return Random(global_force_seed)
725 if threadlocal._hypothesis_global_random is None: # pragma: no cover
726 threadlocal._hypothesis_global_random = Random()
727 seed = threadlocal._hypothesis_global_random.getrandbits(128)
728 wrapped_test._hypothesis_internal_use_generated_seed = seed
729 return Random(seed)
732@dataclass(slots=True, frozen=False)
733class Stuff:
734 selfy: Any
735 args: tuple
736 kwargs: dict
737 given_kwargs: dict
740def process_arguments_to_given(
741 wrapped_test: Any,
742 arguments: Sequence[object],
743 kwargs: dict[str, object],
744 given_kwargs: dict[str, SearchStrategy],
745 params: dict[str, Parameter],
746) -> tuple[Sequence[object], dict[str, object], Stuff]:
747 selfy = None
748 arguments, kwargs = convert_positional_arguments(wrapped_test, arguments, kwargs)
750 # If the test function is a method of some kind, the bound object
751 # will be the first named argument if there are any, otherwise the
752 # first vararg (if any).
753 posargs = [p.name for p in params.values() if p.kind is p.POSITIONAL_OR_KEYWORD]
754 if posargs:
755 selfy = kwargs.get(posargs[0])
756 elif arguments:
757 selfy = arguments[0]
759 # Ensure that we don't mistake mocks for self here.
760 # This can cause the mock to be used as the test runner.
761 if is_mock(selfy):
762 selfy = None
764 arguments = tuple(arguments)
766 with ensure_free_stackframes():
767 for k, s in given_kwargs.items():
768 check_strategy(s, name=k)
769 s.validate()
771 stuff = Stuff(selfy=selfy, args=arguments, kwargs=kwargs, given_kwargs=given_kwargs)
773 return arguments, kwargs, stuff
776def skip_exceptions_to_reraise():
777 """Return a tuple of exceptions meaning 'skip this test', to re-raise.
779 This is intended to cover most common test runners; if you would
780 like another to be added please open an issue or pull request adding
781 it to this function and to tests/cover/test_lazy_import.py
782 """
783 # This is a set in case any library simply re-exports another's Skip exception
784 exceptions = set()
785 # We use this sys.modules trick to avoid importing libraries -
786 # you can't be an instance of a type from an unimported module!
787 # This is fast enough that we don't need to cache the result,
788 # and more importantly it avoids possible side-effects :-)
789 if "unittest" in sys.modules:
790 exceptions.add(sys.modules["unittest"].SkipTest)
791 if "_pytest.outcomes" in sys.modules:
792 exceptions.add(sys.modules["_pytest.outcomes"].Skipped)
793 return tuple(sorted(exceptions, key=str))
796def failure_exceptions_to_catch() -> tuple[type[BaseException], ...]:
797 """Return a tuple of exceptions meaning 'this test has failed', to catch.
799 This is intended to cover most common test runners; if you would
800 like another to be added please open an issue or pull request.
801 """
802 # While SystemExit and GeneratorExit are instances of BaseException, we also
803 # expect them to be deterministic - unlike KeyboardInterrupt - and so we treat
804 # them as standard exceptions, check for flakiness, etc.
805 # See https://github.com/HypothesisWorks/hypothesis/issues/2223 for details.
806 exceptions = [Exception, SystemExit, GeneratorExit]
807 if "_pytest.outcomes" in sys.modules:
808 exceptions.append(sys.modules["_pytest.outcomes"].Failed)
809 return tuple(exceptions)
812def new_given_signature(original_sig, given_kwargs):
813 """Make an updated signature for the wrapped test."""
814 return original_sig.replace(
815 parameters=[
816 p
817 for p in original_sig.parameters.values()
818 if not (
819 p.name in given_kwargs
820 and p.kind in (p.POSITIONAL_OR_KEYWORD, p.KEYWORD_ONLY)
821 )
822 ],
823 return_annotation=None,
824 )
827def default_executor(data, function):
828 return function(data)
831def get_executor(runner):
832 try:
833 execute_example = runner.execute_example
834 except AttributeError:
835 pass
836 else:
837 return lambda data, function: execute_example(partial(function, data))
839 if hasattr(runner, "setup_example") or hasattr(runner, "teardown_example"):
840 setup = getattr(runner, "setup_example", None) or (lambda: None)
841 teardown = getattr(runner, "teardown_example", None) or (lambda ex: None)
843 def execute(data, function):
844 token = None
845 try:
846 token = setup()
847 return function(data)
848 finally:
849 teardown(token)
851 return execute
853 return default_executor
856# This function is a crude solution, a better way of resolving it would probably
857# be to rewrite a bunch of exception handlers to use except*.
858T = TypeVar("T", bound=BaseException)
861def _flatten_group(excgroup: BaseExceptionGroup[T]) -> list[T]:
862 found_exceptions: list[T] = []
863 for exc in excgroup.exceptions:
864 if isinstance(exc, BaseExceptionGroup):
865 found_exceptions.extend(_flatten_group(exc))
866 else:
867 found_exceptions.append(exc)
868 return found_exceptions
871@contextlib.contextmanager
872def unwrap_markers_from_group() -> Generator[None, None, None]:
873 try:
874 yield
875 except BaseExceptionGroup as excgroup:
876 _frozen_exceptions, non_frozen_exceptions = excgroup.split(Frozen)
878 # group only contains Frozen, reraise the group
879 # it doesn't matter what we raise, since any exceptions get disregarded
880 # and reraised as StopTest if data got frozen.
881 if non_frozen_exceptions is None:
882 raise
883 # in all other cases they are discarded
885 # Can RewindRecursive end up in this group?
886 _, user_exceptions = non_frozen_exceptions.split(
887 lambda e: isinstance(e, (StopTest, HypothesisException))
888 )
890 # this might contain marker exceptions, or internal errors, but not frozen.
891 if user_exceptions is not None:
892 raise
894 # single marker exception - reraise it
895 flattened_non_frozen_exceptions: list[BaseException] = _flatten_group(
896 non_frozen_exceptions
897 )
898 if len(flattened_non_frozen_exceptions) == 1:
899 e = flattened_non_frozen_exceptions[0]
900 # preserve the cause of the original exception to not hinder debugging
901 # note that __context__ is still lost though
902 raise e from e.__cause__
904 # multiple marker exceptions. If we re-raise the whole group we break
905 # a bunch of logic so ....?
906 stoptests, non_stoptests = non_frozen_exceptions.split(StopTest)
908 # TODO: stoptest+hypothesisexception ...? Is it possible? If so, what do?
910 if non_stoptests:
911 # TODO: multiple marker exceptions is easy to produce, but the logic in the
912 # engine does not handle it... so we just reraise the first one for now.
913 e = _flatten_group(non_stoptests)[0]
914 raise e from e.__cause__
915 assert stoptests is not None
917 # multiple stoptests: raising the one with the lowest testcounter
918 raise min(_flatten_group(stoptests), key=lambda s_e: s_e.testcounter)
921class StateForActualGivenExecution:
922 def __init__(
923 self,
924 stuff: Stuff,
925 test: Callable[..., Any],
926 settings: Settings,
927 random: Random,
928 wrapped_test: Any,
929 *,
930 thread_overlap: dict[int, bool] | None = None,
931 ):
932 self.stuff = stuff
933 self.test = test
934 self.settings = settings
935 self.random = random
936 self.wrapped_test = wrapped_test
937 self.thread_overlap = {} if thread_overlap is None else thread_overlap
939 self.test_runner = get_executor(stuff.selfy)
940 self.print_given_args = getattr(
941 wrapped_test, "_hypothesis_internal_print_given_args", True
942 )
943 self.known_safe_to_repr = {
944 name
945 for name, strategy in stuff.given_kwargs.items()
946 if strategy == st.data()
947 }
949 self.last_exception = None
950 self.falsifying_examples = ()
951 self.ever_executed = False
952 self.xfail_example_reprs: set[str] = set()
953 self.failed_normally = False
954 self.failed_due_to_deadline = False
956 self.explain_traces: dict[None | InterestingOrigin, set[Trace]] = defaultdict(
957 set
958 )
959 self._start_timestamp = time.time()
960 self._string_repr = ""
961 self._timing_features: dict[str, float] = {}
963 self._runner: ConjectureRunner | None = None
965 @property
966 def test_identifier(self) -> str:
967 return getattr(
968 current_pytest_item.value, "nodeid", None
969 ) or get_pretty_function_description(self.wrapped_test)
971 def _should_trace(self):
972 # NOTE: we explicitly support monkeypatching this. Keep the namespace
973 # access intact.
974 _trace_obs = (
975 observability_enabled() and observability.OBSERVABILITY_COLLECT_COVERAGE
976 )
977 _trace_failure = (
978 self.failed_normally
979 and not self.failed_due_to_deadline
980 and {Phase.shrink, Phase.explain}.issubset(self.settings.phases)
981 )
982 return _trace_obs or _trace_failure
984 def execute_once(
985 self,
986 data,
987 *,
988 print_example=False,
989 is_final=False,
990 expected_failure=None,
991 example_kwargs=None,
992 ):
993 """Run the test function once, using ``data`` as input.
995 If the test raises an exception, it will propagate through to the
996 caller of this method. Depending on its type, this could represent
997 an ordinary test failure, or a fatal error, or a control exception.
999 If this method returns normally, the test might have passed, or
1000 it might have placed ``data`` in an unsuccessful state and then
1001 swallowed the corresponding control exception.
1002 """
1004 self.ever_executed = True
1006 self._string_repr = ""
1007 text_repr = None
1008 if self.settings.deadline is None and not observability_enabled():
1010 @proxies(self.test)
1011 def test(*args, **kwargs):
1012 with unwrap_markers_from_group(), ensure_free_stackframes():
1013 return self.test(*args, **kwargs)
1015 else:
1017 @proxies(self.test)
1018 def test(*args, **kwargs):
1019 arg_drawtime = math.fsum(data.draw_times.values())
1020 arg_stateful = math.fsum(data._stateful_run_times.values())
1021 arg_gctime = gc_cumulative_time()
1022 with unwrap_markers_from_group(), ensure_free_stackframes():
1023 start = time.perf_counter()
1024 try:
1025 result = self.test(*args, **kwargs)
1026 finally:
1027 finish = time.perf_counter()
1028 in_drawtime = math.fsum(data.draw_times.values()) - arg_drawtime
1029 in_stateful = (
1030 math.fsum(data._stateful_run_times.values()) - arg_stateful
1031 )
1032 in_gctime = gc_cumulative_time() - arg_gctime
1033 runtime = finish - start - in_drawtime - in_stateful - in_gctime
1034 self._timing_features = {
1035 "execute:test": runtime,
1036 "overall:gc": in_gctime,
1037 **data.draw_times,
1038 **data._stateful_run_times,
1039 }
1041 if (
1042 (current_deadline := self.settings.deadline) is not None
1043 # we disable the deadline check under concurrent threads, since
1044 # cpython may switch away from a thread for arbitrarily long.
1045 and not self.thread_overlap.get(threading.get_ident(), False)
1046 ):
1047 if not is_final:
1048 current_deadline = (current_deadline // 4) * 5
1049 if runtime >= current_deadline.total_seconds():
1050 raise DeadlineExceeded(
1051 datetime.timedelta(seconds=runtime), self.settings.deadline
1052 )
1053 return result
1055 def run(data: ConjectureData) -> None:
1056 # Set up dynamic context needed by a single test run.
1057 if self.stuff.selfy is not None:
1058 data.hypothesis_runner = self.stuff.selfy
1059 # Generate all arguments to the test function.
1060 args = self.stuff.args
1061 kwargs = dict(self.stuff.kwargs)
1062 if example_kwargs is None:
1063 kw, arglabels = context.prep_args_kwargs_from_strategies(
1064 self.stuff.given_kwargs
1065 )
1066 else:
1067 kw = example_kwargs
1068 arglabels = {}
1069 kwargs.update(kw)
1070 if expected_failure is not None:
1071 nonlocal text_repr
1072 text_repr = repr_call(test, args, kwargs)
1074 if print_example or current_verbosity() >= Verbosity.verbose:
1075 printer = RepresentationPrinter(context=context)
1076 if print_example:
1077 printer.text("Failing test case:")
1078 else:
1079 printer.text("Test case:")
1081 if self.print_given_args:
1082 printer.text(" ")
1083 printer.repr_call(
1084 test.__name__,
1085 args,
1086 kwargs,
1087 force_split=True,
1088 arg_labels=arglabels,
1089 leading_comment=(
1090 "# " + context.data.span_comments[None]
1091 if None in context.data.span_comments
1092 else None
1093 ),
1094 avoid_realization=data.provider.avoid_realization,
1095 known_safe_to_repr=self.known_safe_to_repr,
1096 )
1097 report(printer.getvalue())
1099 if observability_enabled():
1100 printer = RepresentationPrinter(context=context)
1101 printer.repr_call(
1102 test.__name__,
1103 args,
1104 kwargs,
1105 force_split=True,
1106 arg_labels=arglabels,
1107 leading_comment=(
1108 "# " + context.data.span_comments[None]
1109 if None in context.data.span_comments
1110 else None
1111 ),
1112 avoid_realization=data.provider.avoid_realization,
1113 known_safe_to_repr=self.known_safe_to_repr,
1114 )
1115 self._string_repr = printer.getvalue()
1117 try:
1118 return test(*args, **kwargs)
1119 except TypeError as e:
1120 # If we sampled from a sequence of strategies, AND failed with a
1121 # TypeError, *AND that exception mentions SearchStrategy*, add a note:
1122 if (
1123 "SearchStrategy" in str(e)
1124 and data._sampled_from_all_strategies_elements_message is not None
1125 ):
1126 msg, format_arg = data._sampled_from_all_strategies_elements_message
1127 add_note(e, msg.format(format_arg))
1128 raise
1129 finally:
1130 if data._stateful_repr_parts is not None:
1131 self._string_repr = "\n".join(data._stateful_repr_parts)
1133 if observability_enabled():
1134 printer = RepresentationPrinter(context=context)
1135 for name, value in data._observability_args.items():
1136 if name.startswith("generate:Draw "):
1137 try:
1138 value = data.provider.realize(value)
1139 except BackendCannotProceed: # pragma: no cover
1140 value = "<backend failed to realize symbolic>"
1141 printer.text(f"\n{name.removeprefix('generate:')}: ")
1142 printer.pretty(value)
1144 self._string_repr += printer.getvalue()
1146 # self.test_runner can include the execute_example method, or setup/teardown
1147 # _example, so it's important to get the PRNG and build context in place first.
1148 with (
1149 local_settings(self.settings),
1150 deterministic_PRNG(),
1151 BuildContext(
1152 data, is_final=is_final, wrapped_test=self.wrapped_test
1153 ) as context,
1154 ):
1155 # providers may throw in per_case_context_fn, and we'd like
1156 # `result` to still be set in these cases.
1157 result = None
1158 with data.provider.per_test_case_context_manager():
1159 # Run the test function once, via the executor hook.
1160 # In most cases this will delegate straight to `run(data)`.
1161 result = self.test_runner(data, run)
1163 # If a failure was expected, it should have been raised already, so
1164 # instead raise an appropriate diagnostic error.
1165 if expected_failure is not None:
1166 exception, traceback = expected_failure
1167 if isinstance(exception, DeadlineExceeded) and (
1168 runtime_secs := math.fsum(
1169 v
1170 for k, v in self._timing_features.items()
1171 if k.startswith("execute:")
1172 )
1173 ):
1174 report(
1175 "Unreliable test timings! On an initial run, this "
1176 f"test took {exception.runtime.total_seconds() * 1000:.2f}ms, "
1177 "which exceeded the deadline of "
1178 f"{self.settings.deadline.total_seconds() * 1000:.2f}ms, but "
1179 f"on a subsequent run it took {runtime_secs * 1000:.2f} ms, "
1180 "which did not. If you expect this sort of "
1181 "variability in your test timings, consider turning "
1182 "deadlines off for this test by setting deadline=None."
1183 )
1184 else:
1185 report("Failed to reproduce exception. Expected: \n" + traceback)
1186 raise FlakyFailure(
1187 f"Hypothesis {text_repr} produces unreliable results: "
1188 "Failed on the first call but did not on a subsequent one",
1189 [exception],
1190 )
1191 return result
1193 def _flaky_replay_to_failure(
1194 self, err: FlakyReplay, context: BaseException
1195 ) -> FlakyFailure:
1196 assert self._runner is not None
1197 # Note that in the mark_interesting case, _context_ itself
1198 # is part of err._interesting_examples - but it's not in
1199 # _runner.interesting_examples - this is fine, as the context
1200 # (i.e., immediate exception) is appended.
1201 interesting_examples = [
1202 self._runner.interesting_examples[origin]
1203 for origin in err._interesting_origins
1204 if origin in self._runner.interesting_examples
1205 ]
1206 exceptions = [result.expected_exception for result in interesting_examples]
1207 exceptions.append(context) # the immediate exception
1208 return FlakyFailure(err.reason, exceptions)
1210 def _execute_once_for_engine(self, data: ConjectureData) -> None:
1211 """Wrapper around ``execute_once`` that intercepts test failure
1212 exceptions and single-test control exceptions, and turns them into
1213 appropriate method calls to `data` instead.
1215 This allows the engine to assume that any exception other than
1216 ``StopTest`` must be a fatal error, and should stop the entire engine.
1217 """
1218 trace: Trace = frozenset()
1219 backend_cannot_proceed = False
1220 try:
1221 with Tracer(should_trace=self._should_trace()) as tracer:
1222 try:
1223 result = self.execute_once(data)
1224 if (
1225 data.status == Status.VALID and tracer.branches
1226 ): # pragma: no cover
1227 # This is in fact covered by our *non-coverage* tests, but due
1228 # to the settrace() contention *not* by our coverage tests.
1229 self.explain_traces[None].add(tracer.branches)
1230 finally:
1231 trace = tracer.branches
1232 if result is not None:
1233 fail_health_check(
1234 self.settings,
1235 "Tests run under @given should return None, but "
1236 f"{self.test.__name__} returned {result!r} instead.",
1237 HealthCheck.return_value,
1238 )
1239 except UnsatisfiedAssumption as e:
1240 # An "assume" check failed, so instead we inform the engine that
1241 # this test run was invalid.
1242 try:
1243 data.mark_invalid(e.reason)
1244 except FlakyReplay as err:
1245 # This was unexpected, meaning that the assume was flaky.
1246 # Report it as such.
1247 raise self._flaky_replay_to_failure(err, e) from None
1248 except BackendCannotProceed:
1249 # The engine discards this iteration entirely (see engine.py,
1250 # "we're pretending this never happened"), so we shouldn't emit a
1251 # test_case observation for it either -- otherwise an alternative
1252 # backend that aborts before running the test (e.g. crosshair when
1253 # it has exhausted its paths) surfaces a spurious, draw-less
1254 # "passed" observation with an empty representation.
1255 backend_cannot_proceed = True
1256 raise
1257 except StopTest:
1258 # The engine knows how to handle this control exception, so it's
1259 # OK to re-raise it.
1260 raise
1261 except (
1262 FailedHealthCheck,
1263 *skip_exceptions_to_reraise(),
1264 ):
1265 # These are fatal errors or control exceptions that should stop the
1266 # engine, so we re-raise them.
1267 raise
1268 except failure_exceptions_to_catch() as e:
1269 # If an unhandled (i.e., non-Hypothesis) error was raised by
1270 # Hypothesis-internal code, re-raise it as a fatal error instead
1271 # of treating it as a test failure.
1272 if isinstance(e, BaseExceptionGroup) and len(e.exceptions) == 1:
1273 # When a naked exception is implicitly wrapped in an ExceptionGroup
1274 # due to a re-raising "except*", the ExceptionGroup is constructed in
1275 # the caller's stack frame (see #4183). This workaround is specifically
1276 # for implicit wrapping of naked exceptions by "except*", since explicit
1277 # raising of ExceptionGroup gets the proper traceback in the first place
1278 # - there's no need to handle hierarchical groups here, at least if no
1279 # such implicit wrapping happens inside hypothesis code (we only care
1280 # about the hypothesis-or-not distinction).
1281 #
1282 # 01-25-2025: this was patched to give the correct
1283 # stacktrace in cpython https://github.com/python/cpython/issues/128799.
1284 # can remove once python3.11 is EOL.
1285 tb = e.exceptions[0].__traceback__ or e.__traceback__
1286 else:
1287 tb = e.__traceback__
1288 filepath = traceback.extract_tb(tb)[-1][0]
1289 if (
1290 is_hypothesis_file(filepath)
1291 and not isinstance(e, HypothesisException)
1292 # We expect backend authors to use the provider_conformance test
1293 # to test their backends. If an error occurs there, it is probably
1294 # from their backend, and we would like to treat it as a standard
1295 # error, not a hypothesis-internal error.
1296 and not filepath.endswith(
1297 f"internal{os.sep}conjecture{os.sep}provider_conformance.py"
1298 )
1299 ):
1300 raise
1302 if data.frozen:
1303 # This can happen if an error occurred in a finally
1304 # block somewhere, suppressing our original StopTest.
1305 # We raise a new one here to resume normal operation.
1306 raise StopTest(data.testcounter) from e
1307 else:
1308 # The test failed by raising an exception, so we inform the
1309 # engine that this test run was interesting. This is the normal
1310 # path for test runs that fail.
1311 tb = get_trimmed_traceback()
1312 data.expected_traceback = format_exception(e, tb)
1313 data.expected_exception = e
1314 assert data.expected_traceback is not None # for mypy
1315 verbose_report(data.expected_traceback)
1317 self.failed_normally = True
1319 interesting_origin = InterestingOrigin.from_exception(e)
1320 if trace: # pragma: no cover
1321 # Trace collection is explicitly disabled under coverage.
1322 self.explain_traces[interesting_origin].add(trace)
1323 if interesting_origin.exc_type == DeadlineExceeded:
1324 self.failed_due_to_deadline = True
1325 self.explain_traces.clear()
1326 try:
1327 data.mark_interesting(interesting_origin)
1328 except FlakyReplay as err:
1329 raise self._flaky_replay_to_failure(err, e) from None
1331 finally:
1332 # Conditional here so we can save some time constructing the payload; in
1333 # other cases (without coverage) it's cheap enough to do that regardless.
1334 #
1335 # Note that we have to unconditionally realize data.events, because
1336 # the statistics reported by the pytest plugin use a different flow
1337 # than observability, but still access symbolic events.
1339 try:
1340 data.events = data.provider.realize(data.events)
1341 except BackendCannotProceed:
1342 data.events = {}
1344 if observability_enabled() and not backend_cannot_proceed:
1345 if runner := getattr(self, "_runner", None):
1346 phase = runner._current_phase
1347 else: # pragma: no cover # in case of messing with internals
1348 if self.failed_normally or self.failed_due_to_deadline:
1349 phase = "shrink"
1350 else:
1351 phase = "unknown"
1352 backend_desc = f", using backend={self.settings.backend!r}" * (
1353 self.settings.backend != "hypothesis"
1354 and not getattr(runner, "_switch_to_hypothesis_provider", False)
1355 )
1356 try:
1357 data._observability_args = data.provider.realize(
1358 data._observability_args
1359 )
1360 except BackendCannotProceed:
1361 data._observability_args = {}
1363 try:
1364 self._string_repr = data.provider.realize(self._string_repr)
1365 except BackendCannotProceed:
1366 self._string_repr = "<backend failed to realize symbolic arguments>"
1368 try:
1369 data.notes = data.provider.realize(data.notes)
1370 except BackendCannotProceed:
1371 data.notes = []
1373 data.freeze()
1374 tc = make_testcase(
1375 run_start=self._start_timestamp,
1376 property=self.test_identifier,
1377 data=data,
1378 how_generated=f"during {phase} phase{backend_desc}",
1379 representation=self._string_repr,
1380 arguments=data._observability_args,
1381 timing=self._timing_features,
1382 coverage=tractable_coverage_report(trace) or None,
1383 phase=phase,
1384 backend_metadata=data.provider.observe_test_case(),
1385 )
1386 deliver_observation(tc)
1388 for msg in data.provider.observe_information_messages(
1389 lifetime="test_case"
1390 ):
1391 self._deliver_information_message(**msg)
1392 self._timing_features = {}
1394 def _deliver_information_message(
1395 self, *, type: InfoObservationType, title: str, content: str | dict
1396 ) -> None:
1397 deliver_observation(
1398 InfoObservation(
1399 type=type,
1400 run_start=self._start_timestamp,
1401 property=self.test_identifier,
1402 title=title,
1403 content=content,
1404 )
1405 )
1407 def run_engine(self):
1408 """Run the test function many times, on database input and generated
1409 input, using the Conjecture engine.
1410 """
1411 # Tell pytest to omit the body of this function from tracebacks
1412 __tracebackhide__ = True
1413 try:
1414 database_key = self.wrapped_test._hypothesis_internal_database_key
1415 except AttributeError:
1416 if global_force_seed is None:
1417 database_key = function_digest(self.test)
1418 else:
1419 database_key = None
1421 runner = ConjectureRunner(
1422 self._execute_once_for_engine,
1423 settings=self.settings,
1424 random=self.random,
1425 database_key=database_key,
1426 thread_overlap=self.thread_overlap,
1427 )
1428 self._runner = runner
1429 # Use the Conjecture engine to run the test function many times
1430 # on different inputs.
1431 runner.run()
1432 note_statistics(runner.statistics)
1433 if observability_enabled():
1434 self._deliver_information_message(
1435 type="info",
1436 title="Hypothesis Statistics",
1437 content=describe_statistics(runner.statistics),
1438 )
1439 for msg in (
1440 p if isinstance(p := runner.provider, PrimitiveProvider) else p(None)
1441 ).observe_information_messages(lifetime="test_function"):
1442 self._deliver_information_message(**msg)
1444 if runner.call_count == 0:
1445 return
1446 if runner.interesting_examples:
1447 self.falsifying_examples = sorted(
1448 runner.interesting_examples.values(),
1449 key=lambda d: sort_key(d.nodes),
1450 reverse=True,
1451 )
1452 else:
1453 if runner.valid_examples == 0:
1454 explanations = []
1455 if runner.exit_reason is ExitReason.finished:
1456 explanations.append(
1457 "Hypothesis tried every possible input, so the "
1458 "assumptions of this test are impossible to satisfy - "
1459 "not merely unlikely - and running more test cases "
1460 "cannot help."
1461 )
1462 # use a somewhat arbitrary cutoff to avoid recommending spurious
1463 # fixes.
1464 # eg, a few invalid examples from internal filters when the
1465 # problem is the user generating large inputs, or a
1466 # few overruns during internal mutation when the problem is
1467 # impossible user filters/assumes.
1468 if runner.invalid_examples > min(20, runner.call_count // 5):
1469 explanations.append(
1470 f"{runner.invalid_examples} of {runner.call_count} "
1471 "examples failed a .filter() or assume() condition. Try "
1472 "making your filters or assumes less strict, or rewrite "
1473 "using strategy parameters: "
1474 "st.integers().filter(lambda x: x > 0) fails less often "
1475 "(that is, never) when rewritten as st.integers(min_value=1)."
1476 )
1477 if runner.overrun_examples > min(20, runner.call_count // 5):
1478 explanations.append(
1479 f"{runner.overrun_examples} of {runner.call_count} "
1480 "examples were too large to finish generating; try "
1481 "reducing the typical size of your inputs?"
1482 )
1483 rep = get_pretty_function_description(self.test)
1484 raise Unsatisfiable(
1485 f"Unable to satisfy assumptions of {rep}. "
1486 f"{' Also, '.join(explanations)}"
1487 )
1489 # If we have not traced executions, warn about that now (but only when
1490 # we'd expect to do so reliably, i.e. on CPython>=3.12)
1491 if (
1492 hasattr(sys, "monitoring")
1493 and not PYPY
1494 and self._should_trace()
1495 and not Tracer.can_trace()
1496 ): # pragma: no cover
1497 # actually covered by our tests, but only on >= 3.12
1498 warnings.warn(
1499 "avoiding tracing test function because tool id "
1500 f"{MONITORING_TOOL_ID} is already taken by tool "
1501 f"{sys.monitoring.get_tool(MONITORING_TOOL_ID)}.",
1502 HypothesisWarning,
1503 stacklevel=3,
1504 )
1506 if not self.falsifying_examples:
1507 return
1508 elif not (self.settings.report_multiple_bugs and pytest_shows_exceptiongroups):
1509 # Pretend that we only found one failure, by discarding the others.
1510 del self.falsifying_examples[:-1]
1512 # The engine found one or more failures, so we need to reproduce and
1513 # report them.
1515 errors_to_report = []
1517 report_lines = describe_targets(runner.best_observed_targets)
1518 if report_lines:
1519 report_lines.append("")
1521 explanations = explanatory_lines(self.explain_traces, self.settings)
1522 for falsifying_example in self.falsifying_examples:
1523 fragments = []
1525 ran_example = runner.new_conjecture_data(
1526 falsifying_example.choices, max_choices=len(falsifying_example.choices)
1527 )
1528 ran_example.span_comments = falsifying_example.span_comments
1529 tb = None
1530 origin = None
1531 assert falsifying_example.expected_exception is not None
1532 assert falsifying_example.expected_traceback is not None
1533 try:
1534 with with_reporter(fragments.append):
1535 self.execute_once(
1536 ran_example,
1537 print_example=True,
1538 is_final=True,
1539 expected_failure=(
1540 falsifying_example.expected_exception,
1541 falsifying_example.expected_traceback,
1542 ),
1543 )
1544 except StopTest as e:
1545 # Link the expected exception from the first run. Not sure
1546 # how to access the current exception, if it failed
1547 # differently on this run. In fact, in the only known
1548 # reproducer, the StopTest is caused by OVERRUN before the
1549 # test is even executed. Possibly because all initial examples
1550 # failed until the final non-traced replay, and something was
1551 # exhausted? Possibly a FIXME, but sufficiently weird to
1552 # ignore for now.
1553 err = FlakyFailure(
1554 "Inconsistent results: An example failed on the "
1555 "first run but now succeeds (or fails with another "
1556 "error, or is for some reason not runnable).",
1557 # (note: e is a BaseException)
1558 [falsifying_example.expected_exception or e],
1559 )
1560 errors_to_report.append(ReportableError(fragments, err))
1561 except UnsatisfiedAssumption as e: # pragma: no cover # ironically flaky
1562 err = FlakyFailure(
1563 "Unreliable assumption: An example which satisfied "
1564 "assumptions on the first run now fails it.",
1565 [e],
1566 )
1567 errors_to_report.append(ReportableError(fragments, err))
1568 except BaseException as e:
1569 # If we have anything for explain-mode, this is the time to report.
1570 fragments.extend(explanations[falsifying_example.interesting_origin])
1571 error_with_tb = e.with_traceback(get_trimmed_traceback())
1572 errors_to_report.append(ReportableError(fragments, error_with_tb))
1573 tb = format_exception(e, get_trimmed_traceback(e))
1574 origin = InterestingOrigin.from_exception(e)
1575 else:
1576 # execute_once() will always raise either the expected error, or Flaky.
1577 raise NotImplementedError("This should be unreachable")
1578 finally:
1579 ran_example.freeze()
1580 if observability_enabled():
1581 # log our observability line for the final failing test case
1582 tc = make_testcase(
1583 run_start=self._start_timestamp,
1584 property=self.test_identifier,
1585 data=ran_example,
1586 how_generated="minimal failing test case",
1587 representation=self._string_repr,
1588 arguments=ran_example._observability_args,
1589 timing=self._timing_features,
1590 coverage=None, # Not recorded when we're replaying the MFE
1591 status="passed" if sys.exc_info()[0] else "failed",
1592 status_reason=str(origin or "unexpected/flaky pass"),
1593 metadata={"traceback": tb},
1594 )
1595 deliver_observation(tc)
1597 # Whether or not replay actually raised the exception again, we want
1598 # to print the reproduce_failure decorator for the failing test case.
1599 if self.settings.print_blob:
1600 fragments.append(
1601 "\nYou can reproduce this test case by temporarily adding "
1602 f"{reproduction_decorator(falsifying_example.choices)} "
1603 "as a decorator on your test function"
1604 )
1606 _raise_to_user(
1607 errors_to_report,
1608 self.settings,
1609 report_lines,
1610 # A backend might report a failure and then report verified afterwards,
1611 # which is to be interpreted as "there are no more failures *other
1612 # than what we already reported*". Do not report this as unsound.
1613 unsound_backend=(
1614 runner._verified_by_backend
1615 if runner._verified_by_backend and not runner._backend_found_failure
1616 else None
1617 ),
1618 )
1621def _simplify_explicit_errors(errors: list[ReportableError]) -> list[ReportableError]:
1622 """
1623 Group explicit example errors by their InterestingOrigin, keeping only the
1624 simplest one, and adding a note of how many other examples failed with the same
1625 error.
1626 """
1627 by_origin: dict[InterestingOrigin, list[ReportableError]] = defaultdict(list)
1628 for error in errors:
1629 origin = InterestingOrigin.from_exception(error.exception)
1630 by_origin[origin].append(error)
1632 result = []
1633 for group in by_origin.values():
1634 if len(group) == 1:
1635 result.append(group[0])
1636 else:
1637 # Sort by shortlex of representation (first fragment)
1638 def shortlex_key(error):
1639 repr_str = error.fragments[0] if error.fragments else ""
1640 return (len(repr_str), repr_str)
1642 sorted_group = sorted(group, key=shortlex_key)
1643 simplest = sorted_group[0]
1644 other_count = len(group) - 1
1645 add_note(
1646 simplest.exception,
1647 f"(note: {other_count} other explicit example{'s' * (other_count > 1)} "
1648 "also failed with this error; use Verbosity.verbose to view)",
1649 )
1650 result.append(simplest)
1652 return result
1655def _raise_to_user(
1656 errors_to_report, settings, target_lines, trailer="", *, unsound_backend=None
1657):
1658 """Helper function for attaching notes and grouping multiple errors."""
1659 failing_prefix = "Failing test case: "
1660 ls = []
1661 for error in errors_to_report:
1662 for note in error.fragments:
1663 add_note(error.exception, note)
1664 if note.startswith(failing_prefix):
1665 ls.append(note.removeprefix(failing_prefix))
1666 if current_pytest_item.value:
1667 current_pytest_item.value._hypothesis_failing_examples = ls
1669 if len(errors_to_report) == 1:
1670 the_error_hypothesis_found = errors_to_report[0].exception
1671 else:
1672 assert errors_to_report
1673 the_error_hypothesis_found = BaseExceptionGroup(
1674 f"Hypothesis found {len(errors_to_report)} distinct failures{trailer}.",
1675 [error.exception for error in errors_to_report],
1676 )
1678 if settings.verbosity >= Verbosity.normal:
1679 for line in target_lines:
1680 add_note(the_error_hypothesis_found, line)
1682 if unsound_backend:
1683 add_note(
1684 the_error_hypothesis_found,
1685 f"backend={unsound_backend!r} claimed to verify this test passes - "
1686 "please send them a bug report!",
1687 )
1689 raise the_error_hypothesis_found
1692@contextlib.contextmanager
1693def fake_subTest(self, msg=None, **__):
1694 """Monkeypatch for `unittest.TestCase.subTest` during `@given`.
1696 If we don't patch this out, each failing test case is reported as a
1697 separate failing test by the unittest test runner, which is
1698 obviously incorrect. We therefore replace it for the duration with
1699 this version.
1700 """
1701 warnings.warn(
1702 "subTest per-test-case reporting interacts badly with Hypothesis "
1703 "trying hundreds of test cases, so we disable it for the duration of "
1704 "any test that uses `@given`.",
1705 HypothesisWarning,
1706 stacklevel=2,
1707 )
1708 yield
1711@dataclass(slots=False, frozen=False)
1712class HypothesisHandle:
1713 """This object is provided as the .hypothesis attribute on @given tests.
1715 Downstream users can reassign its attributes to insert custom logic into
1716 the execution of each case, for example by converting an async into a
1717 sync function.
1719 This must be an attribute of an attribute, because reassignment of a
1720 first-level attribute would not be visible to Hypothesis if the function
1721 had been decorated before the assignment.
1723 See https://github.com/HypothesisWorks/hypothesis/issues/1257 for more
1724 information.
1725 """
1727 inner_test: Any
1728 _get_fuzz_target: Any
1729 _given_kwargs: Any
1731 @property
1732 def fuzz_one_input(
1733 self,
1734 ) -> Callable[[bytes | bytearray | memoryview | BinaryIO], bytes | None]:
1735 """
1736 Run the test as a fuzz target, driven with the ``buffer`` of bytes.
1738 Depending on the passed ``buffer`` one of three things will happen:
1740 * If the bytestring was invalid, for example because it was too short or was
1741 filtered out by |assume| or |.filter|, |fuzz_one_input| returns ``None``.
1742 * If the bytestring was valid and the test passed, |fuzz_one_input| returns
1743 a canonicalised and pruned bytestring which will replay that |test case|.
1744 This is provided as an option to improve the performance of mutating
1745 fuzzers, but can safely be ignored.
1746 * If the test *failed*, i.e. raised an exception, |fuzz_one_input| will
1747 add the pruned buffer to :ref:`the Hypothesis example database <database>`
1748 and then re-raise that exception. All you need to do to reproduce,
1749 minimize, and de-duplicate all the failures found via fuzzing is run
1750 your test suite!
1752 To reduce the performance impact of database writes, |fuzz_one_input| only
1753 records failing inputs which would be valid shrinks for a known failure -
1754 meaning writes are somewhere between constant and log(N) rather than linear
1755 in runtime. However, this tracking only works within a persistent fuzzing
1756 process; for forkserver fuzzers we recommend ``database=None`` for the main
1757 run, and then replaying with a database enabled if you need to analyse
1758 failures.
1760 Note that the interpretation of both input and output bytestrings is
1761 specific to the exact version of Hypothesis you are using and the strategies
1762 given to the test, just like the :ref:`database <database>` and
1763 |@reproduce_failure|.
1765 Interaction with |@settings|
1766 ----------------------------
1768 |fuzz_one_input| uses just enough of Hypothesis' internals to drive your
1769 test function with a bytestring, and most settings therefore have no effect
1770 in this mode. We recommend running your tests the usual way before fuzzing
1771 to get the benefits of health checks, as well as afterwards to replay,
1772 shrink, deduplicate, and report whatever errors were discovered.
1774 * |settings.database| *is* used by |fuzz_one_input| - adding failures to
1775 the database to be replayed when
1776 you next run your tests is our preferred reporting mechanism and response
1777 to `the 'fuzzer taming' problem <https://blog.regehr.org/archives/925>`__.
1778 * |settings.verbosity| and |settings.stateful_step_count| work as usual.
1779 * The |~settings.deadline|, |~settings.derandomize|, |~settings.max_examples|,
1780 |~settings.phases|, |~settings.print_blob|, |~settings.report_multiple_bugs|,
1781 and |~settings.suppress_health_check| settings do not affect |fuzz_one_input|.
1783 Example Usage
1784 -------------
1786 .. code-block:: python
1788 @given(st.text())
1789 def test_foo(s): ...
1791 # This is a traditional fuzz target - call it with a bytestring,
1792 # or a binary IO object, and it runs the test once.
1793 fuzz_target = test_foo.hypothesis.fuzz_one_input
1795 # For example:
1796 fuzz_target(b"\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00")
1797 fuzz_target(io.BytesIO(b"\\x01"))
1799 .. tip::
1801 If you expect to discover many failures while using |fuzz_one_input|,
1802 consider wrapping your database with |BackgroundWriteDatabase|, for
1803 low-overhead writes of failures.
1805 .. tip::
1807 | Want an integrated workflow for your team's local tests, CI, and continuous fuzzing?
1808 | Use `HypoFuzz <https://hypofuzz.com/>`__ to fuzz your whole test suite, and find more bugs with the same tests!
1810 .. seealso::
1812 See also the :doc:`/how-to/external-fuzzers` how-to.
1813 """
1814 # Note: most users, if they care about fuzzer performance, will access the
1815 # property and assign it to a local variable to move the attribute lookup
1816 # outside their fuzzing loop / before the fork point. We cache it anyway,
1817 # so that naive or unusual use-cases get the best possible performance too.
1818 try:
1819 return self.__cached_target # type: ignore
1820 except AttributeError:
1821 self.__cached_target = self._get_fuzz_target()
1822 return self.__cached_target
1825@overload
1826def given(
1827 _: EllipsisType, /
1828) -> Callable[
1829 [Callable[..., Coroutine[Any, Any, None] | None]], Callable[[], None]
1830]: # pragma: no cover
1831 ...
1834@overload
1835def given(
1836 *_given_arguments: SearchStrategy[Any],
1837) -> Callable[
1838 [Callable[..., Coroutine[Any, Any, None] | None]], Callable[..., None]
1839]: # pragma: no cover
1840 ...
1843@overload
1844def given(
1845 **_given_kwargs: SearchStrategy[Any] | EllipsisType,
1846) -> Callable[
1847 [Callable[..., Coroutine[Any, Any, None] | None]], Callable[..., None]
1848]: # pragma: no cover
1849 ...
1852def given(
1853 *_given_arguments: SearchStrategy[Any] | EllipsisType,
1854 **_given_kwargs: SearchStrategy[Any] | EllipsisType,
1855) -> Callable[[Callable[..., Coroutine[Any, Any, None] | None]], Callable[..., None]]:
1856 """
1857 The |@given| decorator turns a function into a Hypothesis test. This is the
1858 main entry point to Hypothesis.
1860 .. seealso::
1862 See also the :doc:`/tutorial/introduction` tutorial, which introduces
1863 defining Hypothesis tests with |@given|.
1865 .. _given-arguments:
1867 Arguments to ``@given``
1868 -----------------------
1870 Arguments to |@given| may be either positional or keyword arguments:
1872 .. code-block:: python
1874 @given(st.integers(), st.floats())
1875 def test_one(x, y):
1876 pass
1878 @given(x=st.integers(), y=st.floats())
1879 def test_two(x, y):
1880 pass
1882 If using keyword arguments, the arguments may appear in any order, as with
1883 standard Python functions:
1885 .. code-block:: python
1887 # different order, but still equivalent to before
1888 @given(y=st.floats(), x=st.integers())
1889 def test(x, y):
1890 assert isinstance(x, int)
1891 assert isinstance(y, float)
1893 If |@given| is provided fewer positional arguments than the decorated test,
1894 the test arguments are filled in on the right side, leaving the leftmost
1895 positional arguments unfilled:
1897 .. code-block:: python
1899 @given(st.integers(), st.floats())
1900 def test(manual_string, y, z):
1901 assert manual_string == "x"
1902 assert isinstance(y, int)
1903 assert isinstance(z, float)
1905 # `test` is now a callable which takes one argument `manual_string`
1907 test("x")
1908 # or equivalently:
1909 test(manual_string="x")
1911 The reason for this "from the right" behavior is to support using |@given|
1912 with instance methods, by automatically passing through ``self``:
1914 .. code-block:: python
1916 class MyTest(TestCase):
1917 @given(st.integers())
1918 def test(self, x):
1919 assert isinstance(self, MyTest)
1920 assert isinstance(x, int)
1922 If (and only if) using keyword arguments, |@given| may be combined with
1923 ``**kwargs`` or ``*args``:
1925 .. code-block:: python
1927 @given(x=integers(), y=integers())
1928 def test(x, **kwargs):
1929 assert "y" in kwargs
1931 @given(x=integers(), y=integers())
1932 def test(x, *args, **kwargs):
1933 assert args == ()
1934 assert "x" not in kwargs
1935 assert "y" in kwargs
1937 It is an error to:
1939 * Mix positional and keyword arguments to |@given|.
1940 * Use |@given| with a function that has a default value for an argument.
1941 * Use |@given| with positional arguments with a function that uses ``*args``,
1942 ``**kwargs``, or keyword-only arguments.
1944 The function returned by given has all the same arguments as the original
1945 test, minus those that are filled in by |@given|. See the :ref:`notes on
1946 framework compatibility <framework-compatibility>` for how this interacts
1947 with features of other testing libraries, such as :pypi:`pytest` fixtures.
1948 """
1950 if currently_in_test_context():
1951 fail_health_check(
1952 Settings(),
1953 "Nesting @given tests results in quadratic generation and shrinking "
1954 "behavior, and can usually be more cleanly expressed by replacing the "
1955 "inner function with an st.data() parameter on the outer @given."
1956 "\n\n"
1957 "If it is difficult or impossible to refactor this test to remove the "
1958 "nested @given, you can disable this health check with "
1959 "@settings(suppress_health_check=[HealthCheck.nested_given]) on the "
1960 "outer @given. See "
1961 "https://hypothesis.readthedocs.io/en/latest/reference/api.html#hypothesis.HealthCheck "
1962 "for details.",
1963 HealthCheck.nested_given,
1964 )
1966 def run_test_as_given(test):
1967 if inspect.isclass(test):
1968 # Provide a meaningful error to users, instead of exceptions from
1969 # internals that assume we're dealing with a function.
1970 raise InvalidArgument("@given cannot be applied to a class")
1972 if (
1973 "_pytest" in sys.modules
1974 and "_pytest.fixtures" in sys.modules
1975 and (
1976 tuple(map(int, sys.modules["_pytest"].__version__.split(".")[:2]))
1977 >= (8, 4)
1978 )
1979 and isinstance(
1980 test, sys.modules["_pytest.fixtures"].FixtureFunctionDefinition
1981 )
1982 ): # pragma: no cover # covered by pytest/test_fixtures, but not by cover/
1983 raise InvalidArgument("@given cannot be applied to a pytest fixture")
1985 given_arguments = tuple(_given_arguments)
1986 given_kwargs = dict(_given_kwargs)
1988 original_sig = get_signature(test)
1989 if given_arguments == (Ellipsis,) and not given_kwargs:
1990 # user indicated that they want to infer all arguments
1991 given_kwargs = {
1992 p.name: Ellipsis
1993 for p in original_sig.parameters.values()
1994 if p.kind in (p.POSITIONAL_OR_KEYWORD, p.KEYWORD_ONLY)
1995 }
1996 given_arguments = ()
1998 check_invalid = is_invalid_test(
1999 test, original_sig, given_arguments, given_kwargs
2000 )
2002 # If the argument check found problems, return a dummy test function
2003 # that will raise an error if it is actually called.
2004 if check_invalid is not None:
2005 return check_invalid
2007 # Because the argument check succeeded, we can convert @given's
2008 # positional arguments into keyword arguments for simplicity.
2009 if given_arguments:
2010 assert not given_kwargs
2011 posargs = [
2012 p.name
2013 for p in original_sig.parameters.values()
2014 if p.kind is p.POSITIONAL_OR_KEYWORD
2015 ]
2016 given_kwargs = dict(
2017 list(zip(posargs[::-1], given_arguments[::-1], strict=False))[::-1]
2018 )
2019 # These have been converted, so delete them to prevent accidental use.
2020 del given_arguments
2022 new_signature = new_given_signature(original_sig, given_kwargs)
2024 # Use type information to convert "infer" arguments into appropriate strategies.
2025 if ... in given_kwargs.values():
2026 hints = get_type_hints(test)
2027 for name in [name for name, value in given_kwargs.items() if value is ...]:
2028 if name not in hints:
2029 return _invalid(
2030 f"passed {name}=... for {test.__name__}, but {name} has "
2031 "no type annotation",
2032 test=test,
2033 given_kwargs=given_kwargs,
2034 )
2035 given_kwargs[name] = st.from_type(hints[name])
2037 # only raise if the same thread uses two different executors, not if two
2038 # different threads use different executors.
2039 thread_local = ThreadLocal(prev_self=lambda: not_set)
2040 # maps thread_id to whether that thread overlaps in execution with any
2041 # other thread in this @given. We use this to detect whether an @given is
2042 # being run from multiple different threads at once, which informs
2043 # decisions like whether to raise DeadlineExceeded or HealthCheck.too_slow.
2044 thread_overlap: dict[int, bool] = {}
2045 thread_overlap_lock = Lock()
2047 @impersonate(test)
2048 @define_function_signature(test.__name__, test.__doc__, new_signature)
2049 def wrapped_test(*arguments, **kwargs):
2050 # Tell pytest to omit the body of this function from tracebacks
2051 __tracebackhide__ = True
2052 with thread_overlap_lock:
2053 for overlap_thread_id in thread_overlap:
2054 thread_overlap[overlap_thread_id] = True
2056 threadid = threading.get_ident()
2057 # if there are existing threads when this thread starts, then
2058 # this thread starts at an overlapped state.
2059 has_existing_threads = len(thread_overlap) > 0
2060 thread_overlap[threadid] = has_existing_threads
2062 try:
2063 test = wrapped_test.hypothesis.inner_test
2064 if getattr(test, "is_hypothesis_test", False):
2065 raise InvalidArgument(
2066 f"You have applied @given to the test {test.__name__} more than "
2067 "once, which wraps the test several times and is extremely slow. "
2068 "A similar effect can be gained by combining the arguments "
2069 "of the two calls to given. For example, instead of "
2070 "@given(booleans()) @given(integers()), you could write "
2071 "@given(booleans(), integers())"
2072 )
2074 settings = wrapped_test._hypothesis_internal_use_settings
2075 random = get_random_for_wrapped_test(test, wrapped_test)
2076 arguments, kwargs, stuff = process_arguments_to_given(
2077 wrapped_test,
2078 arguments,
2079 kwargs,
2080 given_kwargs,
2081 new_signature.parameters,
2082 )
2084 if (
2085 inspect.iscoroutinefunction(test)
2086 and get_executor(stuff.selfy) is default_executor
2087 ):
2088 # See https://github.com/HypothesisWorks/hypothesis/issues/3054
2089 # If our custom executor doesn't handle coroutines, or we return an
2090 # awaitable from a non-async-def function, we just rely on the
2091 # return_value health check. This catches most user errors though.
2092 raise InvalidArgument(
2093 "Hypothesis doesn't know how to run async test functions like "
2094 f"{test.__name__}. You'll need to write a custom executor, "
2095 "or use a library like pytest-asyncio or pytest-trio which can "
2096 "handle the translation for you.\n See https://hypothesis."
2097 "readthedocs.io/en/latest/details.html#custom-function-execution"
2098 )
2100 runner = stuff.selfy
2101 if isinstance(stuff.selfy, TestCase) and test.__name__ in dir(TestCase):
2102 fail_health_check(
2103 settings,
2104 f"You have applied @given to the method {test.__name__}, which is "
2105 "used by the unittest runner but is not itself a test. "
2106 "This is not useful in any way.",
2107 HealthCheck.not_a_test_method,
2108 )
2109 if bad_django_TestCase(runner): # pragma: no cover
2110 # Covered by the Django tests, but not the pytest coverage task
2111 raise InvalidArgument(
2112 "You have applied @given to a method on "
2113 f"{type(runner).__qualname__}, but this "
2114 "class does not inherit from the supported versions in "
2115 "`hypothesis.extra.django`. Use the Hypothesis variants "
2116 "to ensure that each example is run in a separate "
2117 "database transaction."
2118 )
2120 nonlocal thread_local
2121 # Check selfy really is self (not e.g. a mock) before we health-check
2122 cur_self = (
2123 stuff.selfy
2124 if getattr(type(stuff.selfy), test.__name__, None) is wrapped_test
2125 else None
2126 )
2127 if thread_local.prev_self is not_set:
2128 thread_local.prev_self = cur_self
2129 elif cur_self is not thread_local.prev_self:
2130 fail_health_check(
2131 settings,
2132 f"The method {test.__qualname__} was called from multiple "
2133 "different executors. This may lead to flaky tests and "
2134 "nonreproducible errors when replaying from database."
2135 "\n\n"
2136 "Unlike most health checks, HealthCheck.differing_executors "
2137 "warns about a correctness issue with your test. We "
2138 "therefore recommend fixing the underlying issue, rather "
2139 "than suppressing this health check. However, if you are "
2140 "confident this health check can be safely disabled, you can "
2141 "do so with "
2142 "@settings(suppress_health_check=[HealthCheck.differing_executors]). "
2143 "See "
2144 "https://hypothesis.readthedocs.io/en/latest/reference/api.html#hypothesis.HealthCheck "
2145 "for details.",
2146 HealthCheck.differing_executors,
2147 )
2149 state = StateForActualGivenExecution(
2150 stuff,
2151 test,
2152 settings,
2153 random,
2154 wrapped_test,
2155 thread_overlap=thread_overlap,
2156 )
2158 # If there was a @reproduce_failure decorator, use it to reproduce
2159 # the error (or complain that we couldn't). Either way, this will
2160 # always raise some kind of error.
2161 if (
2162 reproduce_failure := wrapped_test._hypothesis_internal_use_reproduce_failure
2163 ) is not None:
2164 expected_version, failure = reproduce_failure
2165 if expected_version != __version__:
2166 raise InvalidArgument(
2167 "Attempting to reproduce a failure from a different "
2168 f"version of Hypothesis. This failure is from {expected_version}, but "
2169 f"you are currently running {__version__!r}. Please change your "
2170 "Hypothesis version to a matching one."
2171 )
2172 try:
2173 state.execute_once(
2174 ConjectureData.for_choices(decode_failure(failure)),
2175 print_example=True,
2176 is_final=True,
2177 )
2178 raise DidNotReproduce(
2179 "Expected the test to raise an error, but it "
2180 "completed successfully."
2181 )
2182 except StopTest:
2183 raise DidNotReproduce(
2184 "The shape of the test data has changed in some way "
2185 "from where this blob was defined. Are you sure "
2186 "you're running the same test?"
2187 ) from None
2188 except UnsatisfiedAssumption:
2189 raise DidNotReproduce(
2190 "The test data failed to satisfy an assumption in the "
2191 "test. Have you added it since this blob was generated?"
2192 ) from None
2194 # There was no @reproduce_failure, so start by running any explicit
2195 # examples from @example decorators.
2196 if errors := list(
2197 execute_explicit_examples(
2198 state, wrapped_test, arguments, kwargs, original_sig
2199 )
2200 ):
2201 # If we're not going to report multiple bugs, we would have
2202 # stopped running explicit examples at the first failure.
2203 assert len(errors) == 1 or state.settings.report_multiple_bugs
2205 # If an explicit example raised a 'skip' exception, ensure it's never
2206 # wrapped up in an exception group. Because we break out of the loop
2207 # immediately on finding a skip, if present it's always the last error.
2208 if isinstance(errors[-1].exception, skip_exceptions_to_reraise()):
2209 # Covered by `test_issue_3453_regression`, just in a subprocess.
2210 del errors[:-1] # pragma: no cover
2212 if state.settings.verbosity < Verbosity.verbose:
2213 # keep only one error per interesting origin, unless
2214 # verbosity is high
2215 errors = _simplify_explicit_errors(errors)
2217 _raise_to_user(errors, state.settings, [], " in explicit examples")
2219 # If there were any explicit examples, they all ran successfully.
2220 # The next step is to use the Conjecture engine to run the test on
2221 # many different inputs.
2222 ran_explicit_examples = (
2223 Phase.explicit in state.settings.phases
2224 and getattr(wrapped_test, "hypothesis_explicit_examples", ())
2225 )
2226 SKIP_BECAUSE_NO_EXAMPLES = unittest.SkipTest(
2227 "Hypothesis has been told to run no test cases for this test."
2228 )
2229 if not (
2230 Phase.reuse in settings.phases or Phase.generate in settings.phases
2231 ):
2232 if not ran_explicit_examples:
2233 raise SKIP_BECAUSE_NO_EXAMPLES
2234 return
2236 try:
2237 if isinstance(runner, TestCase) and hasattr(runner, "subTest"):
2238 subTest = runner.subTest
2239 try:
2240 runner.subTest = types.MethodType(fake_subTest, runner)
2241 state.run_engine()
2242 finally:
2243 runner.subTest = subTest
2244 else:
2245 state.run_engine()
2246 except BaseException as e:
2247 # The exception caught here should either be an actual test
2248 # failure (or BaseExceptionGroup), or some kind of fatal error
2249 # that caused the engine to stop.
2250 generated_seed = (
2251 wrapped_test._hypothesis_internal_use_generated_seed
2252 )
2253 assert state._runner is not None
2254 stopped_because_slow_shrinking = (
2255 state._runner.statistics.get("stopped-because")
2256 == "shrinking was very slow"
2257 )
2258 with local_settings(settings):
2259 if generated_seed is not None and (
2260 not state.failed_normally or stopped_because_slow_shrinking
2261 ):
2262 pytest_extra_msg = (
2263 (
2264 ", or by running pytest with "
2265 f"--hypothesis-seed={generated_seed}"
2266 )
2267 if running_under_pytest
2268 else ""
2269 )
2270 if stopped_because_slow_shrinking:
2271 msg = (
2272 "\nThis test function exited early because"
2273 " it took too long to shrink. If desired for debugging, "
2274 f"you can reproduce this by adding @seed({generated_seed}) "
2275 f"to this test{pytest_extra_msg}."
2276 )
2277 else:
2278 msg = (
2279 "You can reproduce this failure by adding "
2280 f"@seed({generated_seed}) to this test"
2281 f"{pytest_extra_msg}."
2282 )
2283 report(msg)
2284 # The dance here is to avoid showing users long tracebacks
2285 # full of Hypothesis internals they don't care about.
2286 # We have to do this inline, to avoid adding another
2287 # internal stack frame just when we've removed the rest.
2288 #
2289 # Using a variable for our trimmed error ensures that the line
2290 # which will actually appear in tracebacks is as clear as
2291 # possible - "raise the_error_hypothesis_found".
2292 the_error_hypothesis_found = e.with_traceback(
2293 None
2294 if isinstance(e, BaseExceptionGroup)
2295 else get_trimmed_traceback()
2296 )
2297 raise the_error_hypothesis_found
2299 if not (ran_explicit_examples or state.ever_executed):
2300 raise SKIP_BECAUSE_NO_EXAMPLES
2301 finally:
2302 with thread_overlap_lock:
2303 del thread_overlap[threadid]
2305 def _get_fuzz_target() -> (
2306 Callable[[bytes | bytearray | memoryview | BinaryIO], bytes | None]
2307 ):
2308 # Because fuzzing interfaces are very performance-sensitive, we use a
2309 # somewhat more complicated structure here. `_get_fuzz_target()` is
2310 # called by the `HypothesisHandle.fuzz_one_input` property, allowing
2311 # us to defer our collection of the settings, random instance, and
2312 # reassignable `inner_test` (etc) until `fuzz_one_input` is accessed.
2313 #
2314 # We then share the performance cost of setting up `state` between
2315 # many invocations of the target. We explicitly force `deadline=None`
2316 # for performance reasons, saving ~40% the runtime of an empty test.
2317 test = wrapped_test.hypothesis.inner_test
2318 settings = Settings(
2319 parent=wrapped_test._hypothesis_internal_use_settings, deadline=None
2320 )
2321 random = get_random_for_wrapped_test(test, wrapped_test)
2322 _args, _kwargs, stuff = process_arguments_to_given(
2323 wrapped_test, (), {}, given_kwargs, new_signature.parameters
2324 )
2325 assert not _args
2326 assert not _kwargs
2327 state = StateForActualGivenExecution(
2328 stuff,
2329 test,
2330 settings,
2331 random,
2332 wrapped_test,
2333 thread_overlap=thread_overlap,
2334 )
2335 database_key = function_digest(test) + b".secondary"
2336 # We track the minimal-so-far example for each distinct origin, so
2337 # that we track log-n instead of n examples for long runs. In particular
2338 # it means that we saturate for common errors in long runs instead of
2339 # storing huge volumes of low-value data.
2340 minimal_failures: dict = {}
2342 def fuzz_one_input(
2343 buffer: bytes | bytearray | memoryview | BinaryIO,
2344 ) -> bytes | None:
2345 # This inner part is all that the fuzzer will actually run,
2346 # so we keep it as small and as fast as possible.
2347 if isinstance(buffer, io.IOBase):
2348 buffer = buffer.read(BUFFER_SIZE)
2349 assert isinstance(buffer, (bytes, bytearray, memoryview))
2350 data = ConjectureData(
2351 random=None,
2352 provider=BytestringProvider,
2353 provider_kw={"bytestring": buffer},
2354 )
2355 try:
2356 state.execute_once(data)
2357 status = Status.VALID
2358 except StopTest:
2359 status = data.status
2360 return None
2361 except UnsatisfiedAssumption:
2362 status = Status.INVALID
2363 return None
2364 except BaseException as e:
2365 # The engine sets data.interesting_origin in
2366 # _execute_once_for_engine, but fuzz_one_input calls
2367 # execute_once directly, so we replicate it here.
2368 data.interesting_origin = InterestingOrigin.from_exception(e)
2369 known = minimal_failures.get(data.interesting_origin)
2370 if settings.database is not None and (
2371 known is None or sort_key(data.nodes) <= sort_key(known)
2372 ):
2373 settings.database.save(
2374 database_key, choices_to_bytes(data.choices)
2375 )
2376 minimal_failures[data.interesting_origin] = data.nodes
2377 status = Status.INTERESTING
2378 raise
2379 finally:
2380 if observability_enabled():
2381 data.freeze()
2382 tc = make_testcase(
2383 run_start=state._start_timestamp,
2384 property=state.test_identifier,
2385 data=data,
2386 how_generated="fuzz_one_input",
2387 representation=state._string_repr,
2388 arguments=data._observability_args,
2389 timing=state._timing_features,
2390 coverage=None,
2391 status=status,
2392 backend_metadata=data.provider.observe_test_case(),
2393 )
2394 deliver_observation(tc)
2395 state._timing_features = {}
2397 assert isinstance(data.provider, BytestringProvider)
2398 return bytes(data.provider.drawn)
2400 fuzz_one_input.__doc__ = HypothesisHandle.fuzz_one_input.__doc__
2401 return fuzz_one_input
2403 # After having created the decorated test function, we need to copy
2404 # over some attributes to make the switch as seamless as possible.
2406 for attrib in dir(test):
2407 if not (attrib.startswith("_") or hasattr(wrapped_test, attrib)):
2408 setattr(wrapped_test, attrib, getattr(test, attrib))
2409 wrapped_test.is_hypothesis_test = True
2410 if hasattr(test, "_hypothesis_internal_settings_applied"):
2411 # Used to check if @settings is applied twice.
2412 wrapped_test._hypothesis_internal_settings_applied = True
2413 wrapped_test._hypothesis_internal_use_seed = getattr(
2414 test, "_hypothesis_internal_use_seed", None
2415 )
2416 wrapped_test._hypothesis_internal_use_settings = (
2417 getattr(test, "_hypothesis_internal_use_settings", None) or Settings.default
2418 )
2419 wrapped_test._hypothesis_internal_use_reproduce_failure = getattr(
2420 test, "_hypothesis_internal_use_reproduce_failure", None
2421 )
2422 wrapped_test.hypothesis = HypothesisHandle(test, _get_fuzz_target, given_kwargs)
2423 return wrapped_test
2425 return run_test_as_given
2428def find(
2429 specifier: SearchStrategy[Ex],
2430 condition: Callable[[Any], bool],
2431 *,
2432 settings: Settings | None = None,
2433 random: Random | None = None,
2434 database_key: bytes | None = None,
2435) -> Ex:
2436 """Returns the minimal example from the given strategy ``specifier`` that
2437 matches the predicate function ``condition``."""
2438 if settings is None:
2439 settings = Settings(max_examples=2000)
2440 settings = Settings(
2441 settings, suppress_health_check=list(HealthCheck), report_multiple_bugs=False
2442 )
2444 if database_key is None and settings.database is not None:
2445 # Note: The database key is not guaranteed to be unique. If not, replaying
2446 # of database examples may fail to reproduce due to being replayed on the
2447 # wrong condition.
2448 database_key = function_digest(condition)
2450 if not isinstance(specifier, SearchStrategy):
2451 raise InvalidArgument(
2452 f"Expected SearchStrategy but got {specifier!r} of "
2453 f"type {type(specifier).__name__}"
2454 )
2455 specifier.validate()
2457 last: list[Ex] = []
2459 @settings
2460 @given(specifier)
2461 def test(v):
2462 if condition(v):
2463 last[:] = [v]
2464 raise Found
2466 if random is not None:
2467 test = seed(random.getrandbits(64))(test)
2469 test._hypothesis_internal_database_key = database_key # type: ignore
2471 try:
2472 test()
2473 except Found:
2474 return last[0]
2476 raise NoSuchExample(get_pretty_function_description(condition))