Unit tests integrations

[k0pernicus]

The project needs some unit tests - each new feature has to be tested.

[k0pernicus]

Also, I think that the better solution to test each function/feature is to add unit testing in the documentation of the function, and in a custom file in tests/.

[k0pernicus]

The directory tests/ has been created by @Jean-Serge - merged with commit 74ff12e

[k0pernicus]

The current solution to test private functions/methods is to add the test module inside the source file that contains those private ones.

Example:

// src/my_mod.rs

/// A private function that returns an Option type
fn my_private_function() -> Option<usize> {
...
}

#[cfg(test)]
mod my_private_tests {
    use super::my_private_function;

    /// A function to test my_private_function()
    fn test_my_private_function() {
        ...
    }
}

However, a good practice is to test public functions/methods in a single test unit file, in the tests/ directory.

[Jean-Serge]

Resulting in putting unit tests into the module source file and integration tests into the tests directory.

That way, users could find easily how to use Snatch as a library.