Test a command that uses state

[Nick-Mazuk]

I have a command in Rust that looks like the following:

pub struct AppContext {
    pub response: String,
}

#[tauri::command]
pub fn ping(state: State<'a, AppContext>) -> Result<String, String> {
    Ok(state.response)
}

I'd like to write a unit test for this command. Something that looks like the following:

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

    #[test]
    fn test_pong() {
        let context = AppContext { response: "pong".into() };
        let state = State::new(context); // State's implementation in Tauri is private, so State::new() does not actually exist
        let response = ping(state).unwrap();
        assert_eq!(response, "pong".to_string());
    }
}

From what I can tell looking through Tauri's code is that State's fields are private (so you can't just do State(context)) and everything that creates a State is private.

So it seems like it's impossible to write a unit test for commands?

---

FWIW, with the "test" feature I know it's possible to instead use a mock_builder to instead mock the entire app and invoke commands as shown in this Stackoverflow post. However that opens up a lot more unknowns, and to be honest isn't that developer friendly for high unit test coverage.

See also #8424

[FabianLars]

What about something like this?

#[tauri::command]
fn something(state: tauri::State<String>) -> String {
    state.inner().clone()
}

#[cfg(test)]
mod tests {
    use super::something;
    use tauri::Manager;

    #[test]
    pub fn test_something() {
        let app = tauri::test::mock_app();
        app.manage("something".to_string());
        assert_eq!(&something(app.state::<String>()), "something");
    }
}

I'm no expert but something like State::new() could be problematic because then we'd have to give it a 'static lifetime which doesn't match real behavior and would allow more things than non-static lifetimes. The lifetime in the approach i showed also behaves a bit differently i think but at least it's not static so i hope it's close enough 🤔

[Nick-Mazuk]

Oh awesome, that works perfectly. Thanks Fabian!