Summary - Testing
- Rust course
- Intermediate
- Lesson 88/115
- 5 min
Combine unit, integration and doc tests to test a math crate.
Testing summary
Unit tests are written in src/ in a #[cfg(test)] mod tests module, also reaching private items. Integration tests in the tests/ folder use only the public API. Doc tests run the examples in /// comments. Checks: assert!, assert_eq!, assert_ne!; for an expected panic #[should_panic(expected = "..")]. Tests can also return Result<(), E>, so ? can be used.
Testing with ?
In tests whose setup steps may fail, ? is cleaner than chains of unwrap:
fn yas(s: &str) -> Result<u8, String> {
s.trim().parse().map_err(|e| format!("geçersiz yaş: {e}"))
}
#[test]
fn yas_okunur() -> Result<(), String> {
let y = yas(" 30 ")?;
assert_eq!(y, 30);
Ok(())
}Practice Test returning Result
Write the yas function above and the yas_okunur test returning Result<(), String>. In main, print the result of yas(" 30 ") with {:?}.
Starter code
fn main() {
// buraya yaz
}Sample solution
fn yas(s: &str) -> Result<u8, String> {
s.trim().parse().map_err(|e| format!("geçersiz yaş: {e}"))
}
fn main() {
println!("{:?}", yas(" 30 "));
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn yas_okunur() -> Result<(), String> {
let y = yas(" 30 ")?;
assert_eq!(y, 30);
Ok(())
}
}Expected output
Ok(30)
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What happens if a test returning <code>Result</code> returns <code>Err</code>?
- The test counts as failed and the error is printed Correct answer
- The test counts as passed
- It doesn't compile
- It's skipped
Explanation: #[should_panic] can't be used on tests returning Result; an expected error is written with assert!(r.is_err()).
2 Test return type
#[test]
fn yas_okunur() -> ____ {
let y = yas("30")?;
assert_eq!(y, 30);
Ok(())
}#[test]
fn yas_okunur() -> Result<(), String> {
let y = yas("30")?;
assert_eq!(y, 30);
Ok(())
}Explanation: Tests returning Result can use ?.
3 Group summary
| Term | Meaning |
|---|---|
#[test] |
Test function |
tests/ folder |
Integration test |
/// ``` |
Doc test |
#[should_panic] |
Expected panic |