Viewing file:  assert_that.py (2.75 KB) -rw-r--r--
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import warnings
from typing import Optional, TypeVar, cast, overload
from hamcrest.core.matcher import Matcher
from hamcrest.core.string_description import StringDescription
__author__ = "Jon Reid"
__copyright__ = "Copyright 2011 hamcrest.org"
__license__ = "BSD, see License.txt"
# unittest integration; hide these frames from tracebacks
__unittest = True
# py.test integration; hide these frames from tracebacks
__tracebackhide__ = True
T = TypeVar("T")
@overload
def assert_that(actual: T, matcher: Matcher[T], reason: str = "") -> None:
...
@overload
def assert_that(assertion: bool, reason: str = "") -> None:
...
def assert_that(actual, matcher=None, reason=""):
"""Asserts that actual value satisfies matcher. (Can also assert plain
boolean condition.)
:param actual: The object to evaluate as the actual value.
:param matcher: The matcher to satisfy as the expected condition.
:param reason: Optional explanation to include in failure description.
``assert_that`` passes the actual value to the matcher for evaluation. If
the matcher is not satisfied, an exception is thrown describing the
mismatch.
``assert_that`` is designed to integrate well with PyUnit and other unit
testing frameworks. The exception raised for an unmet assertion is an
:py:exc:`AssertionError`, which PyUnit reports as a test failure.
With a different set of parameters, ``assert_that`` can also verify a
boolean condition:
.. function:: assert_that(assertion[, reason])
:param assertion: Boolean condition to verify.
:param reason: Optional explanation to include in failure description.
This is equivalent to the :py:meth:`~unittest.TestCase.assertTrue` method
of :py:class:`unittest.TestCase`, but offers greater flexibility in test
writing by being a standalone function.
"""
if isinstance(matcher, Matcher):
_assert_match(actual=actual, matcher=matcher, reason=reason)
else:
if isinstance(actual, Matcher):
warnings.warn("arg1 should be boolean, but was {}".format(type(actual)))
_assert_bool(assertion=cast(bool, actual), reason=cast(str, matcher))
def _assert_match(actual: T, matcher: Matcher[T], reason: str) -> None:
if not matcher.matches(actual):
description = StringDescription()
description.append_text(reason).append_text("\nExpected: ").append_description_of(
matcher
).append_text("\n but: ")
matcher.describe_mismatch(actual, description)
description.append_text("\n")
raise AssertionError(description)
def _assert_bool(assertion: bool, reason: Optional[str] = None) -> None:
if not assertion:
if not reason:
reason = "Assertion failed"
raise AssertionError(reason)
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