private async Task <(Guid Otc, string Password)> Collect(Pocket p, params VoucherCreatePayload.VoucherInfo[] vi)
{
int beforeCount = p.VoucherCount;
int requestCount = (from v in vi select v.Count).Sum();
(var otcGen, var pwd) = await _instrument.RequestVouchers(vi);
await p.CollectVouchers(otcGen, pwd);
Assert.AreEqual(beforeCount + requestCount, p.VoucherCount);
return(otcGen, pwd);
}