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92 lines
1.9 KiB
92 lines
1.9 KiB
## Tests and ?
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in Rust 2018, your unit tests can return Result<()>, which lets you use ? in them! This can make them much more concise.
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```rust
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fn sqrt(number: f64) -> Result<f64, String> {
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if number >= 0.0 {
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Ok(number.powf(0.5))
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} else {
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Err("negative floats don't have square roots".to_owned())
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn test_sqrt() -> Result<(), String> {
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let x = 4.0;
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assert_eq!(sqrt(x)?.powf(2.0), x);
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Ok(())
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}
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}
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```
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## Testing panics
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To check functions that should panic under certain circumstances, use attribute #[should_panic]. This attribute accepts optional parameter expected = with the text of the panic message. If your function can panic in multiple ways, it helps make sure your test is testing the correct panic.
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```rust
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pub fn divide_non_zero_result(a: u32, b: u32) -> u32 {
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if b == 0 {
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panic!("Divide-by-zero error");
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} else if a < b {
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panic!("Divide result is zero");
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}
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a / b
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn test_divide() {
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assert_eq!(divide_non_zero_result(10, 2), 5);
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}
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#[test]
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#[should_panic]
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fn test_any_panic() {
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divide_non_zero_result(1, 0);
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}
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#[test]
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#[should_panic(expected = "Divide result is zero")]
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fn test_specific_panic() {
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divide_non_zero_result(1, 10);
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}
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}
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```
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## Ignoring tests
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Tests can be marked with the #[ignore] attribute to exclude some tests. Or to run them with command cargo test -- --ignored
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```rust
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pub fn add(a: i32, b: i32) -> i32 {
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a + b
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn test_add() {
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assert_eq!(add(2, 2), 4);
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}
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#[test]
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fn test_add_hundred() {
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assert_eq!(add(100, 2), 102);
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assert_eq!(add(2, 100), 102);
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}
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#[test]
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#[ignore]
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fn ignored_test() {
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assert_eq!(add(0, 0), 0);
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}
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}
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``` |