pytest-dev/pytest · error · RuntimeError

Unrecognized runpytest option

Error message

Unrecognized runpytest option: {self._method}

What it means

Thrown by Pytester.runpytest() when self._method is neither 'inprocess' nor 'subprocess'. The _method attribute is set from the --runpytest command-line option and should always be one of those two; this guard catches corruption or custom Pytester subclasses.

Solutions

1. Do not set pytester._method manually; rely on the --runpytest={inprocess,subprocess} option.
2. If subclassing, set _method to one of the two documented values.
3. Check for plugins or conftest.py code that patches _method.

Example fix

// before
pytester._method = "custom"
pytester.runpytest()
// after
pytester._method = "subprocess"
pytester.runpytest()

assert pytester._method in ('inprocess', 'subprocess'), f'bad method: {pytester._method}'
pytester.runpytest()

When it happens

Trigger: Subclassing Pytester and overriding _method with an invalid value; manually setting pytester._method; a future pytest version changing the valid set while an old plugin patches _method; the --runpytest option receiving an unknown value through a config override.

Common situations: Custom test harnesses that wrap Pytester; monkeypatching experiments; version skew between pytest and a plugin that touches _method.

Related errors

• could not find test report matching
• Empty parameter set in
• example " " is not found as a file or directory
• Expected a float string for option
• Expected an int string for option

AI-assisted analysis of pytest-dev/pytest@0d6fbdeffa (2026-08-11). Data as JSON: /api/errors/3f3b8dd8e70c10fa. Report an issue: GitHub.

Appendix: source

Thrown at src/_pytest/pytester.py:1219

            sys.stdout.write(out)
            sys.stderr.write(err)

        assert reprec.ret is not None
        res = RunResult(
            reprec.ret, out.splitlines(), err.splitlines(), instant.elapsed().seconds
        )
        res.reprec = reprec  # type: ignore
        return res

    def runpytest(self, *args: str | os.PathLike[str], **kwargs: Any) -> RunResult:
        """Run pytest inline or in a subprocess, depending on the command line
        option "--runpytest" and return a :py:class:`~pytest.RunResult`."""
        new_args = self._ensure_basetemp(args)
        if self._method == "inprocess":
            return self.runpytest_inprocess(*new_args, **kwargs)
        elif self._method == "subprocess":
            return self.runpytest_subprocess(*new_args, **kwargs)
        raise RuntimeError(f"Unrecognized runpytest option: {self._method}")

    def _ensure_basetemp(
        self, args: Sequence[str | os.PathLike[str]]
    ) -> list[str | os.PathLike[str]]:
        new_args = list(args)
        for x in new_args:
            if str(x).startswith("--basetemp"):
                break
        else:
            new_args.append(
                "--basetemp={}".format(self.path.parent.joinpath("basetemp"))
            )
        return new_args

    def parseconfig(self, *args: str | os.PathLike[str]) -> Config:
        """Return a new pytest :class:`pytest.Config` instance from given
        commandline args.

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