What causes "Error importing plugin "{modname}": {e.args[0]}" in pytest-dev/pytest?

Install the missing plugin: pip install .

pytest-dev/pytest · error · ImportError

Error importing plugin "{modname}": {e.args[0]}

Error message

Error importing plugin "{modname}": {e.args[0]}

What it means

When pytest attempts to import a plugin module (via -p NAME, PYTEST_PLUGINS, pytest_plugins in conftest, or entry points) and the import fails with ImportError, pytest re-raises a wrapped ImportError that clearly names the offending plugin. This surfaces broken installs, missing dependencies, or syntax errors in plugin code during startup.

Source

Thrown at src/_pytest/config/__init__.py:927

        importspec = "_pytest." + modname if modname in builtin_plugins else modname
        self.rewrite_hook.mark_rewrite(importspec)

        if consider_entry_points:
            loaded = self.load_setuptools_entrypoints("pytest11", name=modname)
            if loaded:
                return

        try:
            if sys.version_info >= (3, 11):
                mod = importlib.import_module(importspec)
            else:
                # On Python 3.10, import_module breaks
                # testing/test_config.py::test_disable_plugin_autoload.
                __import__(importspec)
                mod = sys.modules[importspec]
        except ImportError as e:
            raise ImportError(
                f'Error importing plugin "{modname}": {e.args[0]}'
            ).with_traceback(e.__traceback__) from e

        except Skipped as e:
            self.skipped_plugins.append((modname, e.msg or ""))
        else:
            self.register(mod, modname)


def _get_plugin_specs_as_list(
    specs: types.ModuleType | str | Sequence[str] | None,
) -> list[str]:
    """Parse a plugins specification into a list of plugin names."""
    # None means empty.
    if specs is None:
        return []
    # Workaround for #3899 - a submodule which happens to be called "pytest_plugins".
    if isinstance(specs, types.ModuleType):

View on GitHub (pinned to 98b357f69e)

Solutions

Install the missing plugin: pip install <plugin_name>.
Check the original ImportError message (e.args[0]) for the root cause (missing module, syntax error, etc.).
Remove the plugin from PYTEST_PLUGINS, addopts, or pytest_plugins if it is no longer needed.
Activate the correct virtualenv where the plugin is installed.

Example fix

# before (pyproject.toml)
[tool.pytest.ini_options]
addopts = '-p pytest_cov'
# but pytest-cov not installed

# after
pip install pytest-cov

Defensive patterns

Strategy: try-catch

Validate before calling

import importlib.util

def can_import_plugin(modname: str) -> bool:
    """Check if a plugin module is importable without side effects."""
    spec = importlib.util.find_spec(modname)
    return spec is not None

Try / catch

import pytest

try:
    exit_code = pytest.main(['-p', 'my_plugin', 'tests/'])
except ImportError as e:
    if 'Error importing plugin' in str(e):
        print(f'Plugin import failed: {e}')
        # install or remove the plugin reference
    raise

Prevention

Pin all plugin dependencies in requirements.txt or pyproject.toml with versions.
Use a dedicated test requirements file installed in CI and local venv.
Run pip install -e '.[dev]' or equivalent before pytest to ensure plugins are present.

When it happens

Trigger: Specifying a plugin that is not installed (e.g., -p pytest_foo when pytest-foo is absent), a plugin with an unmet dependency, or a plugin module with a syntax/import error. importlib.import_module(importspec) raises ImportError and the message is wrapped.

Common situations: Missing pip install for a third-party plugin referenced in pyproject.toml's addopts, a conftest.py listing a plugin in pytest_plugins that isn't installed in the current venv, or a plugin broken by a Python version upgrade.

Related errors

AI-assisted analysis of pytest-dev/pytest@98b357f69e (2026-08-04). Data as JSON: /data/errors/c2a05d2c9c908639.json. Report an issue: GitHub.