Tiny pytest plugin that allows collecting any file regardless of extension. If you don't manually specify test files, this will probably crash.

pytest_allow_extensionless.py

from importlib.util import spec_from_loader, module_from_spec
from importlib.machinery import SourceFileLoader

import pytest


class ModuleWithoutExtension(pytest.Module):
    def _importtestmodule(self):
        print(self.path, type(self.path))
        spec = spec_from_loader(self.path.name, SourceFileLoader(self.path.name, str(self.path)))
        mod = module_from_spec(spec)
        spec.loader.exec_module(mod)

        self.config.pluginmanager.consider_module(mod)
        return mod

def pytest_collect_file(file_path, path, parent):
    return ModuleWithoutExtension.from_parent(parent, path=file_path)