People love to repeat that in Rust "if it compiles, it works". The compiler does kill a whole class of bugs, but it doesn't check your logic. A wrong discount calculation compiles just fine. So does a mixed-up header in a request to a payment API. You still need tests, and writing them in Rust is easy enough: the runner is built into the toolchain, no jest/pytest to install.
A quick look at the basics first, then the painful part: testing code that talks HTTP.
What the language gives you
A minimal test with zero dependencies:
#[cfg(test)]
