Back test

A back test simulates the investment return that an investment strategy would have produced over a specific period.

For example, someone who wanted to evaluate a strategy of buying after stock splits might test the effect of having purchased 500 additional shares in the large-cap stocks in a hypothetical portfolio each time one of the stocks split during the period from 1957 to the present.

Back testing is sometimes used to support a current investment strategy by demonstrating that it would have enjoyed strong past performance. Critics point out that the testing period that's chosen has a significant impact on the results and that past performance doesn't guarantee future returns.