[btasker]

> And finally, tests enable new contributors to work confidently from day one.

Exactly this.

If I run into an issue when using OSS, I tend to try and look at contributing a fix back.

The projects where this is most successful are those with a good range of tests - I don't have the time to sit and learn the workings of a project inside out for the sake of a single fix, a good test suite helps reassure me (and them) that I've not inadvertently broken something.

That same benefit exists for new starters working on closed source codebases - they can hit the ground running much faster, confident that tests will help make sure they don't accidentally blow things up.

But, the OP is also right that tests need to be written in the correct way - built based upon the intent, rather than the code that was actually written (where I can, I tend to try and write a test first - even if I might later need to go back and tweak it)