Rust tip: Improve your testing using context structures

In Rust, we have no default way of achieving setup and teardown functionality like we have in other languages.

But we can utilize Rusts structures to achieve a similar result.

The pattern is simple

• Create a struct (it can contain data if you need it)
• Implement a constructor function for the struct, this will be your setup. Note that you could have several, depending on your different testing needs.
• If you need to do any teardown (in most cases you do not need it). You can implement the drop trait on your struct.

Here is a full example

#[cfg(test)]
mod test {
    struct TestCtx();

    impl TestCtx {
        fn setup() -> Self {
            println!("Setup");

            Self()
        }
    }

    impl Drop for TestCtx {
        fn drop(&mut self) {
            println!("Teardown");
        }
    }

    #[test]
    fn hello_setup_teardown() {
        let _ctx = TestCtx::setup();

        println!("This is my test");

        // Teardown is automatic thanks to Drop
    }
}

And when we run cargo test this we get the following output.

ℹ️ We need to use -- --nocapture to tell cargo not to capture our tests output

❯ cargo test -- --nocapture
   Compiling itesting v0.1.0 (/tmp/tmp.FIXDYeNCdW/itesting)
    Finished test [unoptimized + debuginfo] target(s) in 0.21s
     Running unittests src/main.rs (target/debug/deps/itesting-a8ed9686e842fc47)

running 1 test
Setup
This is my test
Teardown
test test::hello_setup_teardown ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s