11_write_automated_tests

Writing Automated Tests §

The notes reflect the topics in Chapter 11

Unit test §

Rust / Cargo provides built-in support for unit test and integration test. The unit test lib is just like unit-test in Python with nice threading support just like pytest.

// You can have the normal functions above
use super::*; // (4)
 
#[cfg(test)] // (1)
mod tests {
    #[test] // (2)
    fn it_works() {
        let result = 2 + 2;
        assert_eq!(result, 4);
    }
    #[test]
    fn it_works_too() -> Result<(), String> { // (3)
        if 2 + 2 == 4 {
            Ok(())
        } else {
            Err(String::from("two plus two does not equal four"))
        }
    }
}
 

1. The #[cfg(test)] annotation on the tests module tells Rust to compile and run the test code only when you run cargo test, not when you run cargo build. The attribute cfg stands for configuration and tells Rust that the following item should only be included given a certain configuration option. In this case, the configuration option is test, which is provided by Rust for compiling and running tests.

2. This tells cargo test for what function shall be tested.

3. Yeah we can use Result here.

4. In this example, it does not do anything. But you get the idea. Because the tests module is an inner module, we need to bring the code under test in the outer module into the scope of the inner module. We use a glob here so anything we define in the outer module is available to this tests module.

Integration Tests §

Put the test fies in test directory.