Walk the project directory for tests and returns a list.

        :return: list

def _get_files(self):
        """
        Walk the project directory for tests and returns a list.

        :return: list
        """
        excludes = [
            '.git',
            '.tox',
            '.vagrant',
            '.venv',
            os.path.basename(self._config.verifier.directory),
        ]
        generators = [
            util.os_walk(self._config.project_directory, '*.yml', excludes),
            util.os_walk(self._config.project_directory, '*.yaml', excludes),
        ]

        return [f for g in generators for f in g]