Let’s remind ourselves quickly of why this is important to us. There are many answers to this question. For me- if I had to pick the primary appeal of test automation it would be- *spotting problems early*:
If I introduce a bug in my code - I want to know immediately because if I have to debug it a month from now, it might as well have been written by someone else.
To spell out further how test automation helps with this- if you have good test coverage and you run your tests frequently, you’re likely to spot problems that you’ve introduced *quickly*. If you have a discipline of running your tests every time you check in your code, that is called 'continuous integration'.
Other motivations for Test Automation include: you find manual testing tedious, you don't have a QA team, you want to try 'Test Driven Development', etc.