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Description:

pytestrelaxed 2.0.2

pytest-relaxed
pytest-relaxed provides ‘relaxed’ test discovery for pytest.
It is the spiritual successor to https://pypi.python.org/pypi/spec, but is
built for pytest instead of nosetests, and rethinks some aspects of
the design (such as increased ability to opt-in to various behaviors.)
For a development roadmap, see the maintainer’s roadmap page.

Rationale
Has it ever felt strange to you that we put our tests in tests/, then name
the files test_foo.py, name the test classes TestFoo, and finally
name the test methods test_foo_bar? Especially when almost all of the code
inside of tests/ is, well, tests?
This pytest plugin takes a page from the rest of Python, where you don’t have
to explicitly note public module/class members, but only need to hint as to
which ones are private. By default, all files and objects pytest is told to
scan will be considered tests; to mark something as not-a-test, simply prefix
it with an underscore.

Relaxed discovery
The “it’s a test by default unless underscored” approach works for files:
tests
├── _util.py
├── one_module.py
└── another_module.py
It’s applied to module members:
def _helper():
pass

def one_thing():
assert True

def another_thing():
assert False

def yet_another():
assert _helper() == 'something'
And to class members:
class SomeObject:
def behavior_one(self):
assert True

def another_behavior(self):
assert False

def _helper(self):
pass

def it_does_things(self):
assert self._helper() == 'whatever'

Special cases
As you might expect, there are a few more special cases around discovery to
avoid fouling up common test extensions:

Files named conftest.py aren’t treated as tests, because they do special
pytest things;
Module and class members named setup_(module|class|method|function) are
not considered tests, as they are how pytest implements classic/xunit style
setup and teardown;
Objects decorated as fixtures with @pytest.fixture are, of course,
also skipped.

Backwards compatibility
If you like the idea of pytest-relaxed but have a large test suite, it may be
daunting to think about “upgrading” it all in one go. It’s relatively simple to
arrive at a ‘hybrid’ test suite where your legacy tests still run normally (as
long as they’re already pytest-compatible, which is true for most unittest
suites) but ‘relaxed’ style tests also work as expected.

The only change you’ll still have to make is renaming ‘helper’ files (any
whose name doesn’t start with test_) so their names begin with an
underscore; then, of course, search and replace any imports of such files.
pytest-relaxed explicitly sidesteps around anything that looks like
“classic” test files (i.e. named test_*), allowing pytest’s native
collection to take effect. Such files should not need any alteration.
Our reporter (display) functionality still works pretty well with legacy
style tests; test prefixes and suffixes are stripped at display time, so
TestMyThing.test_something still shows up as if it was written in relaxed
style: MyThing w/ nested something.

However, because we don’t collect such tests, nesting and other
features we offer won’t work until you’ve renamed the files to not start
with test_, and changed any classes to not inherit from
unittest.TestCase or similar.

Nested class organization
On top of the relaxed discovery algorithm, pytest-relaxed also lets you
organize tests in a nested fashion, again like the spec nose plugin or the
tools that inspired it, such as Ruby’s rspec.
This is purely optional, but we find it’s a nice middle ground between having a
proliferation of files or suffering a large, flat test namespace making it hard
to see which feature areas have been impacted by a bug (or whatnot).
The feature is enabled by using nested/inner classes, like so:
class SomeObject:
def basic_behavior(self):
assert True

class init:
"__init__"

def no_args_required(self):
assert True

def accepts_some_arg(self):
assert True

def sets_up_config(self):
assert False

class some_method:
def accepts_whatever_params(self):
assert False

def base_behavior(self):
assert True

class when_config_says_foo:
def it_behaves_like_this(self):
assert False

class when_config_says_bar:
def it_behaves_like_this(self):
assert True
Test discovery on these inner classes is recursive, so you can nest them as
deeply as you like. Naturally, as with all Python code, sometimes you can have
too much of a good thing…but that’s up to you.

Nested class attributes
If you’re namespacing your tests via nested classes, you may find yourself
wanting to reference the enclosing “scope” of the outer classes they live in,
such as class attributes. pytest-relaxed automatically copies such attributes
onto inner classes during the test collection phase, allowing you to write code
like this:
class Outer:
behavior_one = True

def outer_test(self):
assert self.behavior_one

class Inner:
behavior_two = True

def inner_test(self):
assert self.behavior_one and self.behavior_two
Notably:

The behavior is nested, infinitely, as you might expect;
Attributes that look like test classes or methods themselves, are not copied
(though others, i.e. ones named with a leading underscore, are);
Only attributes _not_ already present on the inner class are copied; thus
inner classes may naturally “override” attributes, just as with class
inheritance.

Other test helpers
pytest-relaxed offers a few other random lightweight test-related utilities
that don’t merit their own PyPI entries (most ported from spec), such as:

trap, a decorator for use on test functions and/or test
helpers/subroutines which is similar to pytest’s own capsys/capfd
fixtures in that it allows capture of stdout/err.

It offers a slightly simpler API: it replaces sys.(stdout|stderr) with
IO objects which can be getvalue()’d as needed.
More importantly, it can wrap arbitrary callables, which is useful for
code-sharing use cases that don’t easily fit into the design of fixtures.

raises, a wrapper around pytest.raises which works as a decorator,
similar to the Nose testing tool of the same name.

Nested output display
Continuing in the “port of spec / inspired by RSpec and friends” vein,
pytest-relaxed greatly enhances pytest’s verbose display mode:

Tests are shown in a nested, tree-like fashion, with ‘header’ lines shown for
modules, classes (including nested classes) and so forth.
The per-test-result lines thus consist of just the test names, and are
colorized (similar to the built-in verbose mode) based on
success/failure/skip.
Headers and test names are massaged to look more human-readable, such as
replacing underscores with spaces.

Unlike spec, this functionality doesn’t affect normal/non-verbose output
at all, and can be disabled entirely, allowing you to use the relaxed test
discovery alongside normal pytest verbose display or your favorite pytest
output plugins (such as pytest-sugar.)

Installation & use
As with most pytest plugins, it’s quite simple:

pip install pytest-relaxed;
Tell pytest where your tests live via the testpaths option; otherwise
pytest-relaxed will cause pytest to load all of your non-test code as tests!
Not required, but strongly recommended: configure pytest’s default
filename pattern (python_files) to be an unqualified glob (*).

This doesn’t impact (our) test discovery, but pytest’s assertion
‘rewriting’ (the feature that turns assert var == othervar into
assert 17 == 2 during error display) reuses this setting when
determining which files to manipulate.

Thus, a recommended setup.cfg (or pytest.ini, sans the header) is:
[tool:pytest]
testpaths = tests
python_files = *

Write some tests, as exampled above;
pytest to run the tests, and you’re done!