Working with non-python tests¶
A basic example for specifying tests in Yaml files¶
Here is an example conftest.py
(extracted from Ali Afshar’s special purpose pytest-yamlwsgi plugin). This conftest.py
will collect test*.yaml
files and will execute the yaml-formatted content as custom tests:
# content of conftest.py
from __future__ import annotations
import pytest
def pytest_collect_file(parent, file_path):
if file_path.suffix == ".yaml" and file_path.name.startswith("test"):
return YamlFile.from_parent(parent, path=file_path)
class YamlFile(pytest.File):
def collect(self):
# We need a yaml parser, e.g. PyYAML.
import yaml
raw = yaml.safe_load(self.path.open(encoding="utf-8"))
for name, spec in sorted(raw.items()):
yield YamlItem.from_parent(self, name=name, spec=spec)
class YamlItem(pytest.Item):
def __init__(self, *, spec, **kwargs):
super().__init__(**kwargs)
self.spec = spec
def runtest(self):
for name, value in sorted(self.spec.items()):
# Some custom test execution (dumb example follows).
if name != value:
raise YamlException(self, name, value)
def repr_failure(self, excinfo):
"""Called when self.runtest() raises an exception."""
if isinstance(excinfo.value, YamlException):
return "\n".join(
[
"usecase execution failed",
" spec failed: {1!r}: {2!r}".format(*excinfo.value.args),
" no further details known at this point.",
]
)
return super().repr_failure(excinfo)
def reportinfo(self):
return self.path, 0, f"usecase: {self.name}"
class YamlException(Exception):
"""Custom exception for error reporting."""
You can create a simple example file:
# test_simple.yaml
ok:
sub1: sub1
hello:
world: world
some: other
and if you installed PyYAML or a compatible YAML-parser you can now execute the test specification:
nonpython $ pytest test_simple.yaml
=========================== test session starts ============================
platform linux -- Python 3.x.y, pytest-8.x.y, pluggy-1.x.y
rootdir: /home/sweet/project/nonpython
collected 2 items
test_simple.yaml F. [100%]
================================= FAILURES =================================
______________________________ usecase: hello ______________________________
usecase execution failed
spec failed: 'some': 'other'
no further details known at this point.
========================= short test summary info ==========================
FAILED test_simple.yaml::hello
======================= 1 failed, 1 passed in 0.12s ========================
You get one dot for the passing sub1: sub1
check and one failure.
Obviously in the above conftest.py
you’ll want to implement a more
interesting interpretation of the yaml-values. You can easily write
your own domain specific testing language this way.
Note
repr_failure(excinfo)
is called for representing test failures.
If you create custom collection nodes you can return an error
representation string of your choice. It
will be reported as a (red) string.
reportinfo()
is used for representing the test location and is also
consulted when reporting in verbose
mode:
nonpython $ pytest -v
=========================== test session starts ============================
platform linux -- Python 3.x.y, pytest-8.x.y, pluggy-1.x.y -- $PYTHON_PREFIX/bin/python
cachedir: .pytest_cache
rootdir: /home/sweet/project/nonpython
collecting ... collected 2 items
test_simple.yaml::hello FAILED [ 50%]
test_simple.yaml::ok PASSED [100%]
================================= FAILURES =================================
______________________________ usecase: hello ______________________________
usecase execution failed
spec failed: 'some': 'other'
no further details known at this point.
========================= short test summary info ==========================
FAILED test_simple.yaml::hello
======================= 1 failed, 1 passed in 0.12s ========================
While developing your custom test collection and execution it’s also interesting to just look at the collection tree:
nonpython $ pytest --collect-only
=========================== test session starts ============================
platform linux -- Python 3.x.y, pytest-8.x.y, pluggy-1.x.y
rootdir: /home/sweet/project/nonpython
collected 2 items
<Package nonpython>
<YamlFile test_simple.yaml>
<YamlItem hello>
<YamlItem ok>
======================== 2 tests collected in 0.12s ========================