As programmer you should be confident that your code works but for an business you need more than that, you need to prove the code and the assumptions you make

As programmer you should be confident that your code works but for an business you need more than that, you need to prove the code and the assumptions you make with it so that it is safe to rely on. Good programmers understand that tests allow them to move on safely to the next thing, as professional if you are not doing this you are creating technical debt. It feels like your analysis is based on having to add tests without enough support from a skilled tester who is empowered to drive testing, if the tester is just told to rubber stamp code without delaying deployment they wont be able to do much. Thats not really the fault of the tester that is a choice to deprioritise test.