def _get_num_running_containers(containers):
    """
    Gets the total number of currently running docker containers.
    Unit tested: test__get_num_running_containers

    :param containers: The containers found from docker ps.
    :type containers: list
    :returns: The number of containers currently running.
    :rtype int:
    """
    total_running = 0
    for container in containers:
        if container['running']:
            total_running += 1
    return total_running