function doDuring(fn, test, callback) {
    callback = onlyOnce(callback || noop);
    var _fn = wrapAsync(fn);
    var _test = wrapAsync(test);

    function next(err/*, ...args*/) {
        if (err) return callback(err);
        var args = slice(arguments, 1);
        args.push(check);
        _test.apply(this, args);
    }

    function check(err, truth) {
        if (err) return callback(err);
        if (!truth) return callback(null);
        _fn(next);
    }

    check(null, true);

}
The post-check version of [`during`]{@link module:ControlFlow.during}. To reflect the difference in
the order of operations, the arguments `test` and `fn` are switched.

Also a version of [`doWhilst`]{@link module:ControlFlow.doWhilst} with asynchronous `test` function.
@name doDuring
@static
@memberOf module:ControlFlow
@method
@see [async.during]{@link module:ControlFlow.during}
@category Control Flow
@param {AsyncFunction} fn - An async function which is called each time
`test` passes. Invoked with (callback).
@param {AsyncFunction} test - asynchronous truth test to perform before each
execution of `fn`. Invoked with (...args, callback), where `...args` are the
non-error args from the previous callback of `fn`.
@param {Function} [callback] - A callback which is called after the test
function has failed and repeated execution of `fn` has stopped. `callback`
will be passed an error if one occurred, otherwise `null`.