The effort required for a project can scale up if the core concepts of your business are not correctly implemented.
Also, sometimes, it's better to test things out before putting further effort in it. It's important, at this moment, to make sure that your new concept is isolated from the existing system and addressed by an expert, so that it meets the company's requirements regarding the performance, the security, and the quality of your business.
Automated testing in a software is mandatory for developers performance. Manual testing is source of errors, stress, and frustration, for developers and the business teams.
Defining a test strategy is not an easy task, because it requires you to choose in a bunch of solutions: PHPUnit, Atoum, Behat, Robot-Framework, Selenium, Mink, WebDriver, etc.
Also, your testsuite can cover different domains of tests: