CODEWITHSUNDEEP
pythonpython-3.xunit-testinglazy-evaluationpython-hypothesis
SmCaterpillar
SmCaterpillar

Reputation: 7020

Python Hypothesis testing: Is there a way to avoid drawing a LazyStrategy?

If Python hypothesis strategies are too deeply nested, using draw will not create an actual example, but a LazyStrategy. This can be quite problematic at times because the resulting object behaves very differently from an actual example.

Is there a way to enforce eager evaluations of strategies, such that calling draw always returns an actual example of the corresponding strategy?

For example:

from hypothesis import strategies as st

@st.composite
def my_composite_strategy(draw):
    some_example = draw(some_very_complex_deeply_nested_strategy)
    print(type(some_example))
    ...

Will print <class 'hypothesis.strategies._internal.lazy.LazyStrategy'> if executed. What I want instead is <class 'my_module.MyObjectIWriteAStrategyFor'>, so I can use some_example really as if it was a real object.

Upvotes: 0

Views: 821

Answers (1)

Zac Hatfield-Dodds
Zac Hatfield-Dodds

Reputation: 3003

As per https://github.com/HypothesisWorks/hypothesis/issues/3224, your some_very_complex_deeply_nested_strategy is returning a strategy rather than the object you want

Upvotes: 2

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