Dynamic test generation

Normally the test tree is static, defined compile time using modules representing test suites and functions annotated with #[test] defining test cases. Sometimes however it is useful to generate test cases runtime. test-r supports this using the #[test_gen] attribute.

Test generators can be either sync or async (if the tokio feature is enabled). The generator function must take a single parameter, a mutable reference to DynamicTestRegistration. Dependency injection to the generator function is not supported currently, but the dynamically generated tests can use shared dependencies.

The following two examples demonstrate generating sync and async tests using the #[test_gen] attribute:

#![allow(unused)]
fn main() {
use test_r::{add_test, DynamicTestRegistration, TestType, test_gen};

struct Dep1 {
    value: i32,
}

struct Dep2 {
    value: i32,
}

#[test_gen]
fn gen_sync_tests(r: &mut DynamicTestRegistration) {
    println!("Generating some tests with dependencies in a sync generator");
    for i in 0..10 {
        add_test!(
            r,
            format!("test_{i}"),
            TestType::UnitTest,
            move |dep1: &Dep1| {
                println!("Running test {} using dep {}", i, dep1.value);
                let s = i.to_string();
                let i2 = s.parse::<i32>().unwrap();
                assert_eq!(i, i2);
            }
        );
    }
}

#[test_gen]
async fn gen_async_tests(r: &mut DynamicTestRegistration) {
    println!("Generating some async tests with dependencies in a sync generator");
    for i in 0..10 {
        add_test!(
            r,
            format!("test_{i}"),
            TestType::UnitTest,
            move |dep1: &Dep1, d2: &Dep2| async {
                println!("Running test {} using deps {} {}", i, dep1.value, d2.value);
                let s = i.to_string();
                let i2 = s.parse::<i32>().unwrap();
                assert_eq!(i, i2);
            }
        );
    }
}
}

The generator functions are executed at the startup of the test runner, and all the generated tests are added to the test tree. The name of the generated tests must be unique. Each test is added to the test suite the generator function is defined in.