I joined a team recently without a solid test suite or testing practices. Really excited to (gently) spread the gospel of TDD (joking). I have the same thought process though, without tests to back me up I feel exposed.
Less opinionated/experienced with strong type systems though, I do appreciate the flexibility of being able to hack things together to see if they work - then improving upon the solution. strong types seem to make that harder.
I often build systems, then break them up to take the working parts out, then put a subset back together.
The type system is like magnetic Lego that lets you snap pieces together.
With a dynamic system it is really difficult to break things apart and then put them back together (without ever running the code, and with 100% accuracy and immediate feedback).
Less opinionated/experienced with strong type systems though, I do appreciate the flexibility of being able to hack things together to see if they work - then improving upon the solution. strong types seem to make that harder.