pytest-dev/pytest · error · UsageError

Unknown parametrize_long_str_id_strategy: {value!r}. Valid v

Error message

Unknown parametrize_long_str_id_strategy: {value!r}. Valid values: {', '.join(sorted(_LONG_STR_STRATEGIES))}

What it means

Raised as UsageError by IdMaker._get_long_str_strategy when the ini option 'parametrize_long_str_id_strategy' has a value not in the allowed set {'short','sha256','legacy','disallow'}. This option controls how pytest generates test IDs for parametrized values that are long strings/bytes (>100 chars). An invalid value means config parsing accepted it but it is semantically unknown.

Source

Thrown at src/_pytest/python.py:1041

        idval = self._idval_from_hook(val, argname)
        if idval is not None:
            return idval
        if isinstance(val, str | bytes):
            idval = self._apply_long_str_strategy(val, argname, idx)
            if idval is not None:
                return idval
        else:
            idval = self._idval_from_value(val)
            if idval is not None:
                return idval
        return self._idval_from_argname(argname, idx)

    def _get_long_str_strategy(self) -> LongStrIdStrategy:
        if not self.config:
            return "short"
        value = self.config.getini("parametrize_long_str_id_strategy")
        if value not in _LONG_STR_STRATEGIES:
            raise UsageError(
                f"Unknown parametrize_long_str_id_strategy: {value!r}. "
                f"Valid values: {', '.join(sorted(_LONG_STR_STRATEGIES))}"
            )
        return cast(LongStrIdStrategy, value)

    def _apply_long_str_strategy(
        self, val: str | bytes, argname: str, idx: int
    ) -> str | None:
        """Apply the configured strategy for long str/bytes parameter values.

        Only used for auto-generated IDs (not explicit ids=[...] or
        pytest.param(id=...)).
        """
        if len(val) <= 100:
            return _ascii_escaped_by_config(val, self.config)
        match self._get_long_str_strategy():
            case "legacy":
                return _ascii_escaped_by_config(val, self.config)

View on GitHub (pinned to 98b357f69e)

Solutions

Set the option to one of: 'short', 'sha256', 'legacy', or 'disallow'.
Remove the option to fall back to the default ('short').
Check the installed pytest version's docs for the current valid values.

Example fix

// before (pyproject.toml)
[tool.pytest.ini_options]
parametrize_long_str_id_strategy = "hash"
// after
[tool.pytest.ini_options]
parametrize_long_str_id_strategy = "sha256"

Defensive patterns

Strategy: validation

Validate before calling

VALID = {"short", "sha256", "legacy", "disallow"}
val = config.getini("parametrize_long_str_id_strategy")
if val is not None and val not in VALID:
    raise SystemExit(f"parametrize_long_str_id_strategy must be one of {sorted(VALID)}")

Prevention

Use only documented strategy names.
Remove the option to rely on the default.
Re-check valid values after upgrading pytest.

When it happens

Trigger: Setting parametrize_long_str_id_strategy to a typo or unsupported string (e.g. 'none', 'hash', 'truncate') in pyproject.toml [tool.pytest.ini_options], pytest.ini, or tox.ini, then running any parametrized test.

Common situations: Misspelling the strategy name; carrying over a config from a plugin that defined custom strategies; using a value from an outdated docs page.

Related errors

AI-assisted analysis of pytest-dev/pytest@98b357f69e (2026-08-04). Data as JSON: /data/errors/4f3bf2b479f55d5a.json. Report an issue: GitHub.