Acceptance testing is my favorite tool to reach for when working with legacy applications that may have low test quality or no tests at all. Because acceptance testing approaches the application from outside of the source code, we’re able to greatly increase test coverage without having to touch the application’s code itself. Larger teams can use acceptance tests to prove new features behave as expected. For the single developer that knows they should be writing tests but still doesn’t for whatever reason: acceptance testing can help them jump-start their application’s test suite.