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Rust Practices with Rustlings - Tests
Chapter 17 - Tests
Exercise 1
// Tests are important to ensure that your code does what you think it should
// do. Tests can be run on this file with the following command: rustlings run
// tests1
//
// This test has a problem with it -- make the test compile! Make the test pass!
// Make the test fail!
#[cfg(test)]
mod tests {
#[test]
fn you_can_assert() {
assert!();
}
}
The assert!
macro is used to test a condition in a test.
Make the test passed:
#[cfg(test)]
mod tests {
#[test]
fn you_can_assert() {
let first_param = 10;
let second_param = 20;
assert!(first_param < second_param);
}
}
Make the test falied:
#[cfg(test)]
mod tests {
#[test]
fn you_can_assert() {
let first_param = 10;
let second_param = 20;
assert!(first_param > second_param);
}
}
Exercise 2
// This test has a problem with it -- make the test compile! Make the test pass!
// Make the test fail!
#[cfg(test)]
mod tests {
#[test]
fn you_can_assert_eq() {
assert_eq!();
}
}
Quite straight forward, just pass the expected and actual value to the assert_eq!
macro
#[cfg(test)]
mod tests {
#[test]
fn you_can_assert_eq() {
let expected = 10;
let actual = 10;
assert_eq!(expected, actual);
}
}
Exercise 3
// This test isn't testing our function -- make it do that in such a way that
// the test passes. Then write a second test that tests whether we get the
// result we expect to get when we call `is_even(5)`.
pub fn is_even(num: i32) -> bool {
num % 2 == 0
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn is_true_when_even() {
assert!();
}
#[test]
fn is_false_when_odd() {
assert!();
}
}
Solution:
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn is_true_when_even() {
assert!(is_even(2));
}
#[test]
fn is_false_when_odd() {
assert!(!is_even(5));
}
}
Exercise 4
// Make sure that we're testing for the correct conditions!
struct Rectangle {
width: i32,
height: i32
}
impl Rectangle {
// Only change the test functions themselves
pub fn new(width: i32, height: i32) -> Self {
if width <= 0 || height <= 0 {
panic!("Rectangle width and height cannot be negative!")
}
Rectangle {width, height}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn correct_width_and_height() {
// This test should check if the rectangle is the size that we pass into its constructor
let rect = Rectangle::new(10, 20);
assert_eq!(???, 10); // check width
assert_eq!(???, 20); // check height
}
#[test]
fn negative_width() {
// This test should check if program panics when we try to create rectangle with negative width
let _rect = Rectangle::new(-10, 10);
}
#[test]
fn negative_height() {
// This test should check if program panics when we try to create rectangle with negative height
let _rect = Rectangle::new(10, -10);
}
}
To testing a case with panic, we can use should_panic
attribute.
Solution:
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn correct_width_and_height() {
// This test should check if the rectangle is the size that we pass into its constructor
let rect = Rectangle::new(10, 20);
assert_eq!(rect.width, 10); // check width
assert_eq!(rect.height, 20); // check height
}
#[test]
#[should_panic(expected = "Rectangle width and height cannot be negative!")]
fn negative_width() {
// This test should check if program panics when we try to create rectangle with negative width
let _rect = Rectangle::new(-10, 10);
}
#[test]
#[should_panic(expected = "Rectangle width and height cannot be negative!")]
fn negative_height() {
// This test should check if program panics when we try to create rectangle with negative height
let _rect = Rectangle::new(10, -10);
}
}
Conclusion
The 17th chapter of Rustlings - Tests ends here.
TIL:
- How to use tests in Rust: assert, assert_eq, and should_panic
Thanks for reading and please add comments below if you have any questions