Reuse rstest's parametrized cases

:warning: Version 0.5.0 introduce a breaking change

This crate give a way to define a tests set and apply them to every case you need to test. With rstest crate you can define a tests list but if you want to apply the same tests to another test function you must rewrite all cases or write some macros that do the job.

Both solutions have some drawbreak:

• intruduce duplication
• macros makes code harder to read and shift out the focus from tests core

The aim of this crate is solve this problem. rstest_resuse expose two attributes:

• #[template]: to define a template
• #[apply]: to apply a defined template to create tests

Here is a simple example:

use rstest::rstest;
use rstest_reuse::{self, *};
// Here we define the template. This define
// * The test list name to `two_simple_cases`
// * cases: here two cases
#[template]
#[rstest]
#[case(2, 2)]
#[case(4/2, 2)]
// Define a and b as cases arguments
fn two_simple_cases(#[case] a: u32, #[case] b: u32) {}
// Here we apply the `two_simple_cases` template: That is expanded in
// #[template]
// #[rstest]
// #[case(2, 2)]
// #[case(4/2, 2)]
// fn it_works(#[case] a: u32,#[case] b: u32) {
//     assert!(a == b);
// }
#[apply(two_simple_cases)]
fn it_works(a: u32, b: u32) {
    assert!(a == b);
}
// Here we reuse the `two_simple_cases` template to create two 
// other tests
#[apply(two_simple_cases)]
fn it_fail(a: u32, b: u32) {
    assert!(a != b);
}

If we run cargo test we have:

    Finished test [unoptimized + debuginfo] target(s) in 0.05s
     Running target/debug/deps/playground-8a1212f8b5eb00ce
running 4 tests
test it_fail::case_1 ... FAILED
test it_works::case_1 ... ok
test it_works::case_2 ... ok
test it_fail::case_2 ... FAILED
failures:
---- it_fail::case_1 stdout ----
thread 'it_fail::case_1' panicked at 'assertion failed: a != b', src/main.rs:34:5
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
---- it_fail::case_2 stdout ----
thread 'it_fail::case_2' panicked at 'assertion failed: a != b', src/main.rs:34:5
failures:
    it_fail::case_1
    it_fail::case_2
test result: FAILED. 2 passed; 2 failed; 0 ignored; 0 measured; 0 filtered out
error: test failed, to rerun pass '--bin playground'

Simple and neat!

Note that if the test arguments names match the template's ones you can don't repeate the arguments attributes.

Composition and Values

If you need to add some cases or values when apply a template you can leverage on composition. Here a simple example:

#[template]
#[rstest]
#[case(2, 2)]
#[case(4/2, 2)]
fn base(#[case] a: u32, #[case] b: u32) {}

// Here we add a new case and an argument in a value list:
#[apply(base)]
#[case(9/3, 3)]
fn it_works(a: u32, b: u32, #[values("a", "b")] t: &str) {
    assert!(a == b);
    assert!("abcd".contains(t))
}

run 6 tests:

running 6 tests
test it_works::case_1::t_2 ... ok
test it_works::case_2::t_2 ... ok
test it_works::case_2::t_1 ... ok
test it_works::case_3::t_2 ... ok
test it_works::case_3::t_1 ... ok
test it_works::case_1::t_1 ... ok

Template can also used for values and with arguments if you need:

#[template]
#[rstest]
fn base(#[with(42)] fix: u32, #[values(1,2,3)] v: u32) {}

#[fixture]
fn fix(#[default(0)] inner: u32) -> u32 {
    inner
}

#[apply(base)]
fn use_it_with_fixture(fix: u32, v: u32) {
    assert!(fix%v == 0);
}

#[apply(base)]
fn use_it_without_fixture(v: u32) {
    assert!(24 % v == 0);
}

Run also 6 tests:

running 6 tests
test use_it_with_fixture::v_1 ... ok
test use_it_without_fixture::v_1 ... ok
test use_it_with_fixture::v_3 ... ok
test use_it_without_fixture::v_2 ... ok
test use_it_without_fixture::v_3 ... ok
test use_it_with_fixture::v_2 ... ok

Cavelets

use rstest_resuse at the top of your crate

You should add use rstest_resuse at the top of your crate:

#[cfg(test)]
use rstest_reuse;

This is due rstest_reuse::template define a macro that need to call a rstest_resuse's macro. I hope to remove this in the future but for now we should live with it.

Note that

use rstest_reuse::*;

is not enougth: this statment doesn't include rstest_reuse but just its public items.

#[export] Attribute

:warning: Version 0.5.0 introduce a breaking change

Now #[export] attribute give you the possibility to export your template across crates but don't lift the macro definition at the top of your crate (that was the default behaviour prior the 0.5.0 version).

Now if you want put your template at the root of your crate you can define it in the root module or reexport it at the top with something like the following line at the top of your crate:

pub use my::modules::path::of::my::template::my_template;

When you want to export your template you should also take care to declare rstest_reuse as pub at the top of your crate to enable to use it from the modules that would import the template.

So in this case in the crate that would export template you should put at the root of your crate

#[cfg(test)]
pub use rstest_reuse;

And not just use rstest_reuse like in the standard cases.

Dismiss #[macro_use] Attribute Support

:warning: Version 0.5.0 introduce a breaking change

Till version 0.4.0 you can use #[macro_use] to annotate your modules and lift your macro template to the up level. Now rstest leverege only on import and paths like all othter function and original macro is hidden by a random name.

So now if you would use your template from other module you should import it like any other symbol.

mod inner {
    pub(crate) mod sub {
        use rstest_reuse::*;
        #[template]
        #[rstest(a,  b,
            case(2, 2),
            case(4/2, 2),
            )
        ]
        fn two_simple_cases(a: u32, b: u32) {}
    }
}
use rstest_reuse::*;
use rstest::*;

#[apply(inner::sub::two_simple_cases)]
fn it_works_by_path(a: u32, b: u32) {
    assert!(a == b);
}

use inner::sub::two_simple_cases
#[apply(inner::sub::two_simple_cases)]
fn it_works_after_use(a: u32, b: u32) {
    assert!(a == b);
}

Disclamer

This crate is in a development stage. I don't know if I'll include it in rstest or change some syntax in the future.

I did't test it in a lot of cases: if you have some cases where it doesn't works file a ticket on rstest

License

Licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE or license-apache-link)

• MIT license LICENSE-MIT or license-MIT-link at your option.