See how easy it is to get started with automated testing in Laravel There are hundreds of articles on https://dev.to/flippedcoding/4-reasons-you-should-write-tests-first-47oa https://dave.cheney.net/2019/05/14/why-bother-writing-tests-at-all https://www.educative.io/answers/5-reasons-why-testing-code-is-great.
Laravel provides an easy way to make a POST request from your test files using the post() method.
The simplest answer is: Try to write automated tests for all the functionality that you check while manually testing your web app.
There are many other types of tests (Unit tests, Feature tests, Integration tests, Acceptance tests, etc)..