The Auction Sniper Example from Growing Object-Oriented Software Guided by Tests
An Implementation in Ruby
Setting Up the Infrastructure
You need an XMPP server running on localhost. I use prosody, which is simple to setup. After installation, you need to create three users:
sudo prosodyctl register sniper localhost sniper
sudo prosodyctl register auction-item-54321 localhost auction
sudo prosodyctl register auction-item-65432 localhost auction
and should disable the system service:
sudo update-rc.d prosody disable
Then change /etc/prosody/conf.d/localhost.cfg.lua to look like this:
-- Section for localhost
daemonize = false
log = {
{ to = "console" };
}
-- This allows clients to connect to localhost. No harm in it.
VirtualHost "localhost"
All infrastructure services are started through foreman, so run foreman start.
Terms
- Item is something that can be identified and bought
- Bidder is a person or organization that is interested in buying an item
- Bid is a statement that a bidder will pay a given price for an item
- Current price is the current highest bid for the item
- Stop price is the most a bidder is prepared to pay for the item
- Auction is a process for managing bids for an item
- Auction house is an institution that hosts auctions
The Auction Protocol
Bidders send XMPP commands:
- Join: A bidder joins an auction. The sender of the XMPP message identifies the bidder, and the name of the chat session identifies the item.
- Bid: A bidder sends a bidding price to the auction.
Auctions send XMPP events:
- Price: An auction reports the currently accepted price. This event also includes the minimum increment that the next bid must be raised by, and the name of bidder who bid this price. The auction will send this event to a bidder when it joins and to all bidders whenever a new bid has been accepted.
- Close: An auction announces that it has closed. The winner of the last price event has won the auction.