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Description:

pytestiterassert 0.0.3

pytest-iterassert
Have you ever wanted to use all or any in a unit test, but found the assert
message to be lacking? Do assertions on class attributes in collections almost
make you wish you were coding in Java (with a nice assertion framework)? Then
this is the pytest helper for you!
pytest-iterassert provides
all_match and any_match to give you nice asserts.
Examples
The built-in any or
all can cause a lot of
sadness when tests fail:
def test_generator_without_iterassert() -> None:
> assert all(i < 1 for i in range(3))
E assert False
E + where False = all(<genexpr> at 0x10221a250>)

all_match and any_match make debugging easy by hoisting the comparison out,
and printing meaningful debug:
def test_generator_with_iterassert() -> None:
> assert all_match(range(3)) < 1
E assert all(0, 1, 2) < 1
E + where all(0, 1, 2) = all_match(range(0, 3))
E + where range(0, 3) = range(3)

How about a more complex example? Asserting attributes of a class instance is
pretty common.
def test_attr_of_classes_without_iterassert() -> None:
foos = [Foo(1), Foo(2), Foo(3)]
> assert all(foo.bar < 3 for foo in foos)
E assert False
E + where False = all(<genexpr> at 0x10597ca50>)

iterassert makes it easy to apply functions to the iterable, and will convince
pytest to show you the result of that function!
def test_attr_of_classes_with_iterassert_1() -> None:
foos = [Foo(1), Foo(2), Foo(3)]
> assert all_match(foos, get_bar) < 3
E assert all(9001, 9002, 9003) < 3
E + where all(9001, 9002, 9003) = all_match([<Foo(1)>, <Foo(2)>, <Foo(3)>], get_bar)

It's also possible to run more complex checks against all items, by doing the
checking inside a function:
def test_attr_of_classes_with_iterassert_2() -> None:
foos = [Foo(1), Foo(2), Foo(3)]
> assert all_match(foos, check_bar)
E assert all(False, False, False)
E + where all(False, False, False) = all_match([<Foo(1)>, <Foo(2)>, <Foo(3)>], check_bar)

Note in this case, much like the buildin functions, all_match and any_match
take no operator or operand.
And, if you need to incorporate more transformations, but would like to see the
intermediary items, capture allows for this, too:
def test_attr_of_classes_with_iterassert_3() -> None:
foos = [Foo(1), Foo(2), Foo(3)]
> assert all_match(capture(foo.bar for foo in foos), check_val)
E assert all(False, False, False)
E + where all(False, False, False) = all_match([9001, 9002, 9003], check_val)
E + where [9001, 9002, 9003] = capture(<genexpr> at 0x1031220d0>)

Even the test summary says it all:
FAILED example.py::test_generator_without_iterassert - assert False
FAILED example.py::test_generator_with_iterassert - assert all(0, 1, 2) < 1
FAILED example.py::test_attr_of_classes_without_iterassert - assert False
FAILED example.py::test_attr_of_classes_with_iterassert_1 - assert all(9001, 9002, 9003) < 3
FAILED example.py::test_attr_of_classes_with_iterassert_2 - assert all(False, False, False)
FAILED example.py::test_attr_of_classes_with_iterassert_3 - assert all(False, False, False)

Installation
pytest-iterassert is on
PyPI, so you can simply install
via pip install pytest-iterassert (requires Python 3.6 or higher).
(If you're really brave, you can also alias all_match and any_match to the
builtin functions on import.)
Changelog
[0.0.3] - 2020-05-10

Add capture, and allow all_match and any_match to not take an
operator/operand, for checks inside the mapping function

[0.0.2] - 2020-05-07

Initial release

Development
This library uses Poetry for managing
dependencies. You just need to run poetry install, and it will create a
virtual environment with all developer dependencies installed.
Please run poetry run ./lint before submitting pull requests.
License
This library is licensed under the Mozilla Public License Version 2.0. For more
information, see LICENSE.