pytest-dev/pytest · error · TypeError

Unexpected keyword arguments passed to pytest.warns: {argnam

Error message

Unexpected keyword arguments passed to pytest.warns: {argnames}
Use context-manager form instead?

What it means

In context-manager form, pytest.warns accepts only match= as a keyword argument. Any other keyword argument is rejected because there is no function to apply them to.

Source

Thrown at src/_pytest/recwarn.py:163

        Failed: Regex pattern did not match any of the 1 warnings emitted.
         Regex: ...
         Emitted warnings: ...UserWarning...

    **Using with** ``pytest.mark.parametrize``

    When using :ref:`pytest.mark.parametrize ref` it is possible to parametrize tests
    such that some runs raise a warning and others do not.

    This could be achieved in the same way as with exceptions, see
    :ref:`parametrizing_conditional_raising` for an example.

    """
    __tracebackhide__ = True
    if func is None and not args:
        match: str | re.Pattern[str] | None = kwargs.pop("match", None)
        if kwargs:
            argnames = ", ".join(sorted(kwargs))
            raise TypeError(
                f"Unexpected keyword arguments passed to pytest.warns: {argnames}"
                "\nUse context-manager form instead?"
            )
        return WarningsChecker(expected_warning, match_expr=match, _ispytest=True)
    else:
        if not callable(func):
            raise TypeError(f"{func!r} object (type: {type(func)}) must be callable")
        with WarningsChecker(expected_warning, _ispytest=True):
            return func(*args, **kwargs)


class WarningsRecorder(warnings.catch_warnings):
    """A context manager to record raised warnings.

    Each recorded warning is an instance of :class:`warnings.WarningMessage`.

    Adapted from `warnings.catch_warnings`.

View on GitHub (pinned to 98b357f69e)

Solutions

1. Use only the match= keyword in context-manager form; remove unknown kwargs.
2. If you meant to pass arguments to a function, use the function-call form: pytest.warns(UserWarning, my_func, arg1, arg2).
3. Check the pytest version docs — the parameter may have been renamed or removed.

Example fix

// before
pytest.warns(UserWarning, match='x', messege='y')
// after
pytest.warns(UserWarning, match='x')

allowed = {'match'}
bad = set(kwargs) - allowed
if bad:
    raise TypeError(f'unexpected kwargs for context-manager form: {sorted(bad)}')
pytest.warns(UserWarning, match=kwargs.get('match'))

When it happens

Trigger: Calling pytest.warns(UserWarning, foo='bar') or pytest.warns(UserWarning, match='x', extra=1). Hits recwarn.py:163 when kwargs remain after popping match.

Common situations: Typo in a kwarg name (e.g. 'metch'); passing function arguments via kwargs intended for the function-call form; passing a deprecated/removed parameter.

Related errors

• {func!r} object (type: {type(func)}) must be callable
• exceptions must be derived from Warning, not %s
• Warning must be str or Warning, got {msg!r} (type {type(msg)
• absolute tolerance can't be NaN.
• relative tolerance can't be negative: {relative_tolerance}

AI-assisted analysis of pytest-dev/pytest@98b357f69e (2026-08-04). Data as JSON: /data/errors/54136c0ed6022be9.json. Report an issue: GitHub.