I started a react component library project that has been going for 4 years now and gets about 40k downloads a month. If it wasn't for my test suite, things would have been a giant mess long ago and I probably would have abandoned it. I can't think of doing a react project without a test suite because over time, any dependencies you have (including on react) will end up breaking things in ways that you don't know. Wi…
The nature of a personal project is such that I may not come back to it for months, sometimes even years. The first thing I always do is run the test suite. It's my lodestar. It helps me understand what state the project is in so I can confidently pick up where I had left it.
It is also my requirements documentation - as code.