Function raises

sklearn/utils/_testing.py:1075–1112

Context manager to ensure exceptions are raised within a code block. This is similar to and inspired from pytest.raises, but supports a few other cases. This is only intended to be used in estimator_checks.py where we don't want to use pytest. In the rest of the code base, just use

(expected_exc_type, match=None, may_pass=False, err_msg=None)

def raises(expected_exc_type, match=None, may_pass=False, err_msg=None):
    """Context manager to ensure exceptions are raised within a code block.

    This is similar to and inspired from pytest.raises, but supports a few
    other cases.

    This is only intended to be used in estimator_checks.py where we don't
    want to use pytest. In the rest of the code base, just use pytest.raises
    instead.

    Parameters
    ----------
    excepted_exc_type : Exception or list of Exception
        The exception that should be raised by the block. If a list, the block
        should raise one of the exceptions.
    match : str or list of str, default=None
        A regex that the exception message should match. If a list, one of
        the entries must match. If None, match isn't enforced.
    may_pass : bool, default=False
        If True, the block is allowed to not raise an exception. Useful in
        cases where some estimators may support a feature but others must
        fail with an appropriate error message. By default, the context
        manager will raise an exception if the block does not raise an
        exception.
    err_msg : str, default=None
        If the context manager fails (e.g. the block fails to raise the
        proper exception, or fails to match), then an AssertionError is
        raised with this message. By default, an AssertionError is raised
        with a default error message (depends on the kind of failure). Use
        this to indicate how users should fix their estimators to pass the
        checks.

    Attributes
    ----------
    raised_and_matched : bool
        True if an exception was raised and a match was found, False otherwise.
    """
    return _Raises(expected_exc_type, match, may_pass, err_msg)


class _Raises(contextlib.AbstractContextManager):