Type systems can be thought of as low-cost (in terms of dev time) declarative tests. Which should leave you with less to test in your actual tests. They also give much quicker feedback than tests.
Is TypeScript low-cost? Most TS projects I've worked on had at least a 10 to 30 seconds build waiting time per iteration. This means that every time I make a change and run the tests, I need to wait 10 to 30 seconds.
With my iterative test-driven approach, I probably iterate about once every minute on average (also, my development iteration time gets faster as I become more experienced in the project). So 30 seconds represents 50% of my total development time. Meaning that I could have written 50% more tests or 50% more features in the same amount of time. And that's not even accounting for my loss of focus incurred as a result of waiting 30 seconds to see the result of my code change. By the time I see the result, the concept in my mind is not as fresh as it was 30 seconds earlier.
Are you aware of tsc options like --watch and --incremental ?
Combined with other live-reloading tools like nodemon or jest --watch you can have almost the same speed of your development-test-run-debug loops as in plain JS. But you do gain an additional instant feedback channel from the compiler.
No longer enjoying programming is a cost nobody can afford to pay. When I read the long list of c#, I mean typescript documentation, it gives me PTSD from c# and java, which people used to hate here, but now suddenly like and let me tell you it has nothing to do with microsoft social engineering.
