Use of Mock Values in Rust - Home

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Mocking¶

https://crates.io/crates/mailtutan

Mocking in Rust: Mockall and alternatives
mockall
mockers
turmoil Turmoil is a framework for testing distributed systems. It provides deterministic execution by running multiple concurrent hosts within a single thread. It introduces “hardship” into the system via changes in the simulated network. The network can be controlled manually or with a seeded rng.

Tips and Traps¶

Mock values can be helpful sometimes especially for testing. For example, I had a function which takes rng: &mut dyn RngCore as a parameter. However, for certain combination of other parameters, rng is not used at all. For those cases, it is perfectly OK to pass in a mock RNG value.

struct FakeRng {}

impl RngCore for FakeRng {
    fn next_u32(&mut self) -> u32 {
        todo!()
    }

    fn next_u64(&mut self) -> u64 {
        todo!()
    }

    fn fill_bytes(&mut self, dest: &mut [u8]) {
        todo!()
    }

    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), rand::Error> {
        todo!()
    }
}