The first homework for https://class.coursera.org/compinvesting1-2012-001/ involves using hindsight to pick 4 equities from that performed well and calculate performance metrics, e.g. the Sharpe ratio, if the student had allocated a percent of their portfolio to each of those stocks.
The next step is to use something that can be a proxy for actual paper trading, like Yahoo or Google Finance.
This is an example of how to use Quantopian to do the paper trading exercise.
I calculate how many shares to order based on the initial price and what percentage we want to allocate to the equity.
After the initial buys, the algorithm does nothing but waits to see the returns!