Speeding up Selenium with Application Mocks` is a technique that combines parallel testing grids with application mocks to improve the performance of functional tests in Selenium. By removing the back end from the application, creating an application mock, and using optimized infrastructure, test runs can be completed faster without causing delays in application releases. This approach offers several benefits, including faster testing, fewer delays, less time cost for failed tests, faster iterations on front-end bugs, and continuous testing. However, it also has some downsides, such as the inability to identify back-end to front-end related bugs and ongoing maintenance requirements. The initial setup of the mock environment requires some work, but is worthwhile in exchange for the benefits. The process involves deploying the current version of the application to a limited infrastructure, wiring up the integration setup, modifying the application, and configuring Sauce Connect and log analysis on the testing infrastructure. This approach can be applied to web applications and mobile applications with API capabilities, allowing front-end developers to test their code continuously and preventing failed test runs or slow Selenium scripts from delaying releases.