Otherwise, tests have a cost just like any other code. You can see this by looking at both extremes: perfect tests (described above) and useless tests. For example, tests that make your codebase too brittle, tests that don't actually test anything useful, spending too much time writing tests, spending a lot of time writing tests for precisely the code with high disposability, tests that are too coupled with the code, stupid tests that should be removed but won't be because tests tend to be append-only, etc.

Testing is an advanced topic where every +1 unit you spend on testing doesn't mean your application is now +1 unit more robust. +1 unit of time spent in tests can even mean your application is -2 units worse because testing is a trade-off.

So tests are more than capable of hamstringing your unlaunched MVP. They're also capable of being the reason you launched your MVP sooner than later. But the costs of testing are no illusion.