Once in a while every Pythonista faces a need to test that some string value matches a regex pattern. When it comes we have no option but to use
re module directly.import re
def test_something_very_useful():
value = get_some_string()
assert re.match('\d+', value)
While it works fine in case of lone string, it's not always convenient to do the same when a string is a part of more complex data structure (e.g.
dict), because you need to extract the string, check it and only then get back to check rest attributes.import re
def test_something_even_more_useful():
mapping = get_some_structure()
# inconvenient and boring! :(
assert 'value' in mapping
value = mapping.pop('value')
assert re.match('\d+', value)
# rest assertion
assert mapping = {'foo': 1,
'bar': 2}
Fortunately, it's pretty easy to write convenient
pytest helper that would check a pattern as a part of checking the whole data structure.def test_something_even_more_useful():
mapping = get_some_structure()
assert mapping = {'foo': 1,
'bar': 2,
'value': pytest_regex('\d+')}
Looks better, huh? :) So the trick is done by the following few lines which we're successfully using in XSnippet API.
import re
class pytest_regex:
"""Assert that a given string meets some expectations."""
def __init__(self, pattern, flags=0):
self._regex = re.compile(pattern, flags)
def __eq__(self, actual):
return bool(self._regex.match(actual))
def __repr__(self):
return self._regex.pattern
Well, actually, it's not by any means tied to
pytest and could be used even in non-test production code, though I found this rather queer.from : https://kalnytskyi.com/howto/assert-str-matches-regex-in-pytest/
