It’s the 101 of talking about testing, it’s been discussed to the death. As usual, “it’s a trade-off”.
You’re right that writing tests can make shipping a feature slower. However, already having tests makes shipping a feature faster (higher confidence it works, less manual testing of the feature and the adjacent ones). It also lowers the amount of bugs, which are going to slow down delivery of new features. They also increase maintenance cost though (tests are code that needs maintenance too).
Is it worth it? Depends, although it’s quite rare that no test at all is the right trade off
You’re right that writing tests can make shipping a feature slower. However, already having tests makes shipping a feature faster (higher confidence it works, less manual testing of the feature and the adjacent ones). It also lowers the amount of bugs, which are going to slow down delivery of new features. They also increase maintenance cost though (tests are code that needs maintenance too).
Is it worth it? Depends, although it’s quite rare that no test at all is the right trade off