[−][src]Attribute Macro rstest::rstest

#[rstest]

The attribute that you should use for your tests. Your annotated function's arguments can be injected with [fixture]s, provided by parametrized cases or by value lists.

General Syntax

rstest attribute can be applied to any function and you can costumize its parameters by the follow syntax

rstest(
    arg_1,
    ...,
    arg_n[,]
    [::attribute_1[:: ... [::attribute_k]]]
)

Where:

  • arg_i could be one of the follow
    • ident that match to one of function arguments (see parametrized cases for more details)
    • case[::description](v1, ..., vl) a test case (see parametrized cases for more details)
    • fixture(v1, ..., vl) where fixture is one of function arguments that and v1, ..., vl is a partial list of fixture's arguments (see injecting fixtures] for more details)
    • ident => [v1, ..., vl] where ident is one of function arguments and v1, ..., vl is a list of values for ident (see value lists for more details)
  • attribute_j a test attribute

Function's arguments can be present just once as case identity, fixture or value list.

Your test function can use generics, impl or dyn and like any kind of rust tests:

  • return results
  • marked by #[should_panic] attribute

Injecting Fixtures

The simplest case is write a test that can be injected with [fixture]s. You can just declare all used fixtures by passing them as a function's arguments. This can help your test to be neat and make your dependecy clear.

use rstest::*;

#[fixture]
fn injected() -> i32 { 42 }

#[rstest]
fn the_test(injected: i32) {
    assert_eq!(42, injected)
}

[rstest] proc_macro will desugar it to something that isn't so far from

#[test]
fn the_test() {
    let injected=injected();
    assert_eq!(42, injected)
}

Sometimes is useful to have some parametes in your fixtures but your test would override the fixture's default values in some cases. Like in fixture partial injection you can indicate some fixture's arguments also in rstest.

use rstest::*;
 
#[fixture]
fn name() -> &'static str { "Alice" }
#[fixture]
fn age() -> u8 { 22 }
 
#[fixture]
fn user(name: impl AsRef<str>, age: u8) -> User { User(name.as_ref().to_owned(), age) }
 
#[rstest(user("Bob"))]
fn check_user(user: User) {
    assert_eq("Bob", user.name())
}

Test Parametrized Cases

If you would execute your test for a set of input data cases you can define the arguments to use and the cases list. Let see the classical Fibonacci example. In this case we would give the input value and the expected result for a set of cases to test.

use rstest::rstest;

#[rstest(input, expected,
    case(0, 0),
    case(1, 1),
    case(2, 1),
    case(3, 2),
    case(4, 3),
)]
fn fibonacci_test(input: u32, expected: u32) {
    assert_eq!(expected, fibonacci(input))
}

fn fibonacci(input: u32) -> u32 {
    match input {
        0 => 0,
        1 => 1,
        n => fibonacci(n - 2) + fibonacci(n - 1)
    }
}

rstest will produce a 5 indipendent tests and not just one that check every case. Every test can fail indipendently and cargo test will give follow output:

running 5 tests
test fibonacci_test::case_1 ... ok
test fibonacci_test::case_2 ... ok
test fibonacci_test::case_3 ... ok
test fibonacci_test::case_4 ... ok
test fibonacci_test::case_5 ... ok
 
test result: ok. 5 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

The cases input values can be arbitrary Rust expresions that return the argument type.

use rstest::rstest;
  
fn sum(a: usize, b: usize) -> usize { a + b }
 
#[rstest(s, len,
    case("foo", 3),
    case(String::from("foo"), 2 + 1),
    case(format!("foo"), sum(2, 1)),
)]
fn test_len(s: impl AsRef<str>, len: usize) {
    assert_eq!(s.as_ref().len(), len);
}

Optional case description

Optionally you can give a description to every case simple by follow case with ::my_case_description where my_case_description should be a a valid Rust ident.

#[rstest(input, expected,
    case::zero_base_case(0, 0),
    case::one_base_case(1, 1),
    case(2, 1),
    case(3, 2),
)]

Outuput will be

running 4 tests
test fibonacci_test::case_1_zero_base_case ... ok
test fibonacci_test::case_2_one_base_case ... ok
test fibonacci_test::case_3 ... ok
test fibonacci_test::case_4 ... ok
 
test result: ok. 4 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

Values Lists

Another useful way to write a test and execute it for some values is to use the values list syntax. This syntax can be usefull both for a plain list and for testing all combination of input arguments.

 
#[rstest(input => ["Jhon", "alice", "My_Name", "Zigy_2001"])]
fn should_be_valid(input: &str) {
    assert!(is_valid(input))
}

or


#[rstest(
    name => ["J", "A", "A________________________________________21"],
    age => [14, 100], // Maybe more than 100 is an error or joke
)]
fn should_accept_all_corner_cases(name: &str, age: u8) {
    assert!(valid_user(name, age))
}

where cargo test output is

running 6 tests
test should_accept_all_corner_cases::name_1::age_1 ... ok
test should_accept_all_corner_cases::name_3::age_1 ... ok
test should_accept_all_corner_cases::name_3::age_2 ... ok
test should_accept_all_corner_cases::name_2::age_1 ... ok
test should_accept_all_corner_cases::name_2::age_2 ... ok
test should_accept_all_corner_cases::name_1::age_2 ... ok
 
test result: ok. 6 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

Putting all Together

All these features can be used together: take some fixtures, define some fixed cases and, for each case, tests all combinations of given values. For istance you need to test that given your repository in cases of both logged in or guest user should return an invalid query error.

 
use rstest::*;
 
#[fixture]
fn repository() -> InMemoryRepository {
    let mut r = InMemoryRepository::default();
    // fill repository by some data
    r
}
 
#[fixture]
fn alice() -> User {
    User::logged("Alice", "2001-10-04", "London", "UK")
}
 
#[rstest(user,
    case::logged_user(alice()), // We can use `fixture` also as standard function
    case::guest(User::Guest),   // We can give a name to every case : `guest` in this case
    query => ["     ", "^%$#@!", "...." ]
)]
#[should_panic(expected = "Invalid query error")] // We whould test a panic
fn should_be_invalid_query_error(repository: impl Repository, user: User, query: &str) {
    repository.find_items(&user, query).unwrap();
}

Attributes

Trace Input Arguments

Sometimes can be very helpful to print all test's input arguments. To do it you can use the trace parameter.

use rstest::*;

#[fixture]
fn injected() -> i32 { 42 }

#[rstest(::trace)]
fn the_test(injected: i32) {
    assert_eq!(42, injected)
}

Will print an output like

Testing started at 14.12 ...
------------ TEST ARGUMENTS ------------
injected = 42
-------------- TEST START --------------


Expected :42
Actual   :43

If you want to trace input arguments but skip some of them that don't implement the Debug trait, you can also use the notrace(list, of, inputs) attribute:

#[rstest(::trace::notrace(xzy, have_no_sense))]
fn the_test(injected: i32, xyz: Xyz, have_no_sense: NoSense) {
    assert_eq!(42, injected)
}