Test

Overall, Rust provides a relatively simple but comprehensive testing facility that suits a test-driven development model. Unfortunately, at the author’s workplace, most release cycles have too few people and too many requirements, so test-driven development is not practical. Adding unit and integration tests later, when there is finally time for testing, becomes very troublesome.

Comprehension

• Basic syntax

  
  pub fn greeting(name: &str) -> String {
      String::from("Hello!")
  }
  
  pub struct Guess {
      value: i32,
  }
  
  impl Guess {
      pub fn new(value: i32) -> Guess {
          if value < 1 || value > 100 {
              panic!("Guess value must be between 1 and 100, got {}.", value);
          }
  
          Guess { value }
      }
  }
  
  #[cfg(test)]
  mod tests {
  	use super::*;
      #[test]
      fn it_works() {
  			// assert_ne! is also available
          assert_eq!(2 + 2, 4);
      }
  
  	#[test]
      fn will_fail() {
          panic!("Make this test fail");
      }
  
  	#[test]
      fn greeting_contains_name() {
          let result = greeting("Carol");
  			// print a hint when an assertion does not meet expectations
          assert!(
              result.contains("Carol"),
              "Greeting did not contain name, value was `{}`",
              result
          );
      }
  
  	#[test]
  	#[should_panic]
  	// should_panic checks whether a panic occurs
  	fn greater_than_100() {
          Guess::new(200);
      }
  }
  
  #[cfg(test)]
  mod tests2 {
      #[test]
  	// when returning Result<T, E>, the should_panic attribute cannot be used
      fn it_works() -> Result<(), String> {
          if 2 + 2 == 4 {
              Ok(())
          } else {
              Err(String::from("two plus two does not equal four"))
          }
      }
  }
  

Origin

https://doc.rust-lang.org/book/ch11-00-testing.html