Function assert_warns

numpy/testing/_private/utils.py:1726–1777

Fail unless the given callable throws the specified warning. A warning of class warning_class should be thrown by the callable when invoked with arguments args and keyword arguments kwargs. If a different type of warning is thrown, it will not be caught. If called with all arg

(warning_class, *args, **kwargs)

def assert_warns(warning_class, *args, **kwargs):
    """
    Fail unless the given callable throws the specified warning.

    A warning of class warning_class should be thrown by the callable when
    invoked with arguments args and keyword arguments kwargs.
    If a different type of warning is thrown, it will not be caught.

    If called with all arguments other than the warning class omitted, may be
    used as a context manager:

        with assert_warns(SomeWarning):
            do_something()

    The ability to be used as a context manager is new in NumPy v1.11.0.

    .. versionadded:: 1.4.0

    Parameters
    ----------
    warning_class : class
        The class defining the warning that `func` is expected to throw.
    func : callable, optional
        Callable to test
    *args : Arguments
        Arguments for `func`.
    **kwargs : Kwargs
        Keyword arguments for `func`.

    Returns
    -------
    The value returned by `func`.

    Examples
    --------
    >>> import warnings
    >>> def deprecated_func(num):
    ...     warnings.warn("Please upgrade", DeprecationWarning)
    ...     return num*num
    >>> with np.testing.assert_warns(DeprecationWarning):
    ...     assert deprecated_func(4) == 16
    >>> # or passing a func
    >>> ret = np.testing.assert_warns(DeprecationWarning, deprecated_func, 4)
    >>> assert ret == 16
    """
    if not args:
        return _assert_warns_context(warning_class)

    func = args[0]
    args = args[1:]
    with _assert_warns_context(warning_class, name=func.__name__):
        return func(*args, **kwargs)


@contextlib.contextmanager