Conclusion
In this chapter, we have discussed many of the options that Rust has for testing code. We have discussed some strategies of how to split tests into different tiers, so that local development can be snappy while testing runs in CI can be extensive. We have looked at some randomized testing methods like property testing, fuzzing and mutation testing and showed how they can be used to gain confidence that code behaves correctly in the face of untrusted inputs. We have explored how to handle external services when writing well-tested code. We have also covered how to measure how much of the code is covered during testing.
In my opinion, testing is very valuable for writing robust code. Especially approaches that take little effort but produce great test coverage (such as randomized testing) can help make sure that code really does behave well.