TokensToGold

Sometime I need to assert some predicate on all of an iterable, and for that the builtin functions all/any are great - but the failure messages aren't useful at all! For example - the same test written in three ways:

• A generator expression

    def test_all_even():
        even_stevens = list(range(1,100,2))
>       assert all(is_even(number) for number in even_stevens)
E       assert False
E        +  where False = all(<generator object test_all_even.<locals>.<genexpr> at 0x101f82ed0>)

• A list comprehension

    def test_all_even():
        even_stevens = list(range(1,100,2))
>       assert all([is_even(number) for number in even_stevens])
E       assert False
E        +  where False = all([False, False, False, False, False, False, ...])

• A for loop

    def test_all_even():
        even_stevens = list(range(1,100,2))
        for number in even_stevens:
>           assert is_even(number)
E           assert False
E            +  where False = is_even(1)

test_all_any.py:7: AssertionError

The only one that gives a meaningful report is the for loop - but it's way more wordy, and all asserts don't translate to a for loop nicely (I'll have to write a break or a helper function - yuck) I propose the assertion re-writer "unrolls" the iterator to the third form, and then uses the already existing reports.

• Include a detailed description of the bug or suggestion
• pip list of the virtual environment you are using

Package        Version
-------------- -------
atomicwrites   1.3.0  
attrs          19.1.0 
more-itertools 7.0.0  
pip            19.0.3 
pluggy         0.9.0  
py             1.8.0  
pytest         4.4.0  
setuptools     40.8.0 
six            1.12.0 

• pytest and operating system versions platform darwin -- Python 3.7.3, pytest-4.4.0, py-1.8.0, pluggy-0.9.0
• Minimal example if possible