    def test_uses_existing_file_and_ignores_xdg(self):
        with WindowsSafeTempDir() as d:
            default_db_file_location = os.path.join(self.home, '.b2_account_info')
            open(default_db_file_location, 'a').close()
            account_info = self._make_sqlite_account_info(
                env={
                    'HOME': self.home,
                    'USERPROFILE': self.home,
                    XDG_CONFIG_HOME_ENV_VAR: d,
                }
            )
            actual_path = os.path.abspath(account_info.filename)
            assert default_db_file_location == actual_path
            assert not os.path.exists(os.path.join(d, 'b2'))
The software checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check. This can cause the software to perform invalid actions when the resource is in an unexpected state.