Major search engines test every release against a list of search queries. You could start with https://trends.google.com/trends/topcharts. You should have an automated test script with a list of (query, good URL) pairs and make sure the good URL appears in the top few results.
Not just for demos, but to help you hack. You can make a small change to the algorithm and re-run the test and see if the score goes up or down. It's very convenient for testing changes deep inside the code.
