Use Fuzz Testing to find issues with the code
Fuzz testing (fuzzing) is a quality assurance technique used to discover coding errors and security loopholes in software, operating systems, or networks. It involves inputting massive amounts of random data, called fuzz, to the test subject in an attempt to make it crash.
This is usually a technique done with Automation to see how fields respond to random text and interactions.
Manual testers may want to use Bug Magnet, a popular Chrome Extenstion to add random data to fields. This is more exploratory testing than Fuzz Testing. Fuzz Testing is focused more on how the software reacts to a huge set of random data being entered.
Fuzzing is a critical part of testing as it checks for potential vulnerabilities with the software application and logic.
You can learn more about Fuzzing at the Open Web Application Security Project Foundation website.