darve.sh

A cheat sheet for cargo test

The assert macros, plus the flags to run one test, run tests in order, or show output.

2 min read#rust#test

The #[cfg(test)] annotation tells Rust to run the function only when cargo test is run and not when cargo build is run

Functions#

rust
assert!(1 == 2, "wasn't true"); //it will print wasn't true when test fails
assert_eq!(6, 6);
assert_ne!(6, 5);

Run test#

sh
cargo test

Run tests in parallel or consecutively#

sh
cargo test -- --test-threads=<numbers>

Change output capture behavior, show logs#

sh
cargo test -- --nocapture

Run single or multiple tests#

sh
cargo test <function-name|pattern>
rust
pub fn add_one(num: i64) -> i64 {
    num + 1
}

pub fn add_two(num: i64) -> i64 {
    num + 2
}

#[cfg(test)]
mod tests {
	use super::*;
	#[test]
	fn add_one_test() {
		assert_eq!!(4, add_one(3));
	}

	#[test]
	fn add_two_test() {
		assert_eq!(6, add_two(4));
	}
}

Example

bash
//will run only one test
cargo test add_one_test
//will run all tests starting with add_
cargo test add_

Test function that should panic#

use #[should_panic] attribute

rust
pub fn i_panic() {
    panic!("omg!");
}

#[cfg(test)]
mod test {
    use super::*;
    #[test]
    #[should_panic]
    fn should_panic() {
        i_panic();
    }
}

//The above test will pass

Ignore a test#

Use #[ignore] attribute

Integration tests#

Make a directory called tests at the root level of the project. Assume you have this code in the lib.rs file in the project adder

rust
/*
|-adder/src
  |--lib.rs
*/
pub add_two(num: i64) -> i64{
	num + 2
}

tests/integration_test.rs

rust
extern crate adder;

#[test]
fn add_two_test(){
	assert_eq!(6, adder::add_two(4));
}

We don't need to use #[cfg(test)] here. When running cargo test, it will run both unit and integration tests. You can also run only tests from a particular integration test file. In the above example, if you want to run tests from integration_test.ts file

rust
cargo test --test integration_test.rs