For the following test
# bad_test.py
from datetime import datetime
from hypothesis import given, strategies as st, assume
@given(start_date=st.datetimes(), data=st.data())
def test_foo(start_date, data):
end_date = data.draw(st.datetimes(min_value=start_date))
assert Falseyou will sometimes give you a scary NotImplementedError: This should never happen error raised in hypothesis.internal.conjecture.shrinker.
Full traceback
Traceback (most recent call last):
File "bad_test.py", line 31, in <module>
test_foo()
File "bad_test.py", line 26, in test_foo
def test_foo(start_date, data):
File ".../hypothesis/hypothesis-python/src/hypothesis/core.py", line 1471, in wrapped_test
raise the_error_hypothesis_found
File ".../hypothesis/hypothesis-python/src/hypothesis/core.py", line 1438, in wrapped_test
state.run_engine()
File ".../hypothesis/hypothesis-python/src/hypothesis/core.py", line 1006, in run_engine
runner.run()
File ".../hypothesis/hypothesis-python/src/hypothesis/internal/conjecture/engine.py", line 461, in run
self._run()
File ".../hypothesis/hypothesis-python/src/hypothesis/internal/conjecture/engine.py", line 874, in _run
self.shrink_interesting_examples()
File ".../hypothesis/hypothesis-python/src/hypothesis/internal/conjecture/engine.py", line 939, in shrink_interesting_examples
self.shrink(example, predicate)
File ".../hypothesis/hypothesis-python/src/hypothesis/internal/conjecture/engine.py", line 971, in shrink
s.shrink()
File ".../hypothesis/hypothesis-python/src/hypothesis/internal/conjecture/shrinker.py", line 442, in shrink
self.explain()
File ".../hypothesis/hypothesis-python/src/hypothesis/internal/conjecture/shrinker.py", line 578, in explain
raise NotImplementedError("This should never happen")
NotImplementedError: This should never happen
I never see this issue once .hypothesis is generated, but if it's not (e.g. if you keep on deleting it before running the tests again) then I see it more often than not.
This looks to be an issue from #3749, as I get this issue on the latest release/master, but not on say the 6.84.2 release just before the aforementioned explain-mode patch.
This was found in a PyCon UK "sprint" I ran with someone who's never used the library before—not the best timing 😅 Huge kudos to @End-of-Eternity for giving me a minimal reproducer!
For the following test
you will sometimes give you a scary
NotImplementedError: This should never happenerror raised inhypothesis.internal.conjecture.shrinker.Full traceback
I never see this issue once
.hypothesisis generated, but if it's not (e.g. if you keep on deleting it before running the tests again) then I see it more often than not.This looks to be an issue from #3749, as I get this issue on the latest release/
master, but not on say the6.84.2release just before the aforementioned explain-mode patch.This was found in a PyCon UK "sprint" I ran with someone who's never used the library before—not the best timing 😅 Huge kudos to @End-of-Eternity for giving me a minimal reproducer!