This crate provides #[test_case]
procedural macro attribute that generates multiple parametrized tests using one body with different input parameters.
A test is generated for each data set passed in test_case
attribute.
Under the hood, all test cases that share same body are grouped into mod
, giving clear and readable test results.
First of all you have to add this dependency to your Cargo.toml
:
[dev-dependencies]
test-case = "0.3.3"
Additionally you have to import the procedural macro with use
statement:
use test_case::test_case;
The crate depends on proc_macro
feature that has been stabilized on rustc 1.29+.
#![cfg(test)]
extern crate test_case;
use test_case::test_case;
#[test_case( 2, 4 ; "when both operands are possitive")]
#[test_case( 4, 2 ; "when operands are swapped")]
#[test_case(-2, -4 ; "when both operands are negative")]
fn multiplication_tests(x: i8, y: i8) {
let actual = (x * y).abs();
assert_eq!(8, actual)
}
Output from cargo test
for this example:
$ cargo test
running 3 tests
test multiplication_tests::when_both_operands_are_possitive ... ok
test multiplication_tests::when_both_operands_are_negative ... ok
test multiplication_tests::when_operands_are_swapped ... ok
test result: ok. 3 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out
If your only assertion is just assert_eq!
, you can pass the expectation as macro attribute using =>
syntax:
#[test_case( 2 => 2 ; "returns given number for positive input")]
#[test_case(-2 => 2 ; "returns opposite number for non-positive input")]
#[test_case( 0 => 0 ; "returns 0 for 0")]
fn abs_tests(x: i8) -> i8 {
if x > 0 { x } else { -x }
}
Which is equivalent to
#[test_case( 2, 2 ; "returns given number for positive input")]
#[test_case(-2, 2 ; "returns opposite number for non-positive input")]
#[test_case( 0, 0 ; "returns 0 for 0")]
fn abs_tests(x: i8, expected: i8){
let actual = if x > 0 { x } else { -x };
assert_eq!(expected, actual);
}
Attributes and expectation may be any expresion unless they contain =>
, e.g.
#[test_case(None, None => 0 ; "treats none as 0")]
#[test_case(Some(2), Some(3) => 5)]
#[test_case(Some(2 + 3), Some(4) => 2 + 3 + 4)]
fn fancy_addition(x: Option<i8>, y: Option<i8>) -> i8 {
x.unwrap_or(0) + y.unwrap_or(0)
}
Note: in fact, =>
is not prohibited but the parser will always treat last =>
sign as beginning of expectation definition.
Test case names are optional. They are set using ;
followed by string literal at the end of macro attributes.
Example generated code:
mod fancy_addition {
#[allow(unused_imports)]
use super::*;
fn fancy_addition(x: Option<i8>, y: Option<i8>) -> i8 {
x.unwrap_or(0) + y.unwrap_or(0)
}
#[test]
fn treats_none_as_0() {
let expected = 0;
let actual = fancy_addition(None, None);
assert_eq!(expected, actual);
}
#[test]
fn some_2_some_3() {
let expected = 5;
let actual = fancy_addition(Some(2), Some(3));
assert_eq!(expected, actual);
}
#[test]
fn some_2_3_some_4() {
let expected = 2 + 3 + 4;
let actual = fancy_addition(Some(2 + 3), Some(4));
assert_eq!(expected, actual);
}
}
If test case name (passed using ;
syntax described above) contains word "inconclusive", generated test will be marked with #[ignore]
.
#[test_case("42")]
#[test_case("XX" ; "inconclusive - parsing letters temporarily doesn't work but it's ok")]
fn parses_input(input: &str) {
// ...
}
Generated code:
mod parses_input {
// ...
#[test]
pub fn _42() {
// ...
}
#[test]
#[ignore]
pub fn inconclusive_parsing_letters_temporarily_doesn_t_work_but_it_s_ok() {
// ...
}
Note: word inconclusive
is only reserved in test name given after ;
.
Licensed under of MIT license (LICENSE-MIT or https://opensource.org/licenses/MIT)
All contributions and comments are more than welcome! Don't be afraid to open an issue or PR whenever you find a bug or have an idea to improve this crate.
Recommended tools:
cargo readme
- to regenerate README.md based on template and lib.rs commentscargo insta
- to review test snapshotscargo edit
- to add/remove dependenciescargo fmt
- to format codecargo clippy
- for all insights and tipscargo fix
- for fixing warnings