verify-call 0.3.0

Utility to verify whether a method has been called on a mock.
Documentation 
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#![warn(missing_docs)]
#![warn(rustdoc::missing_doc_code_examples)]
#![warn(missing_debug_implementations)]
#![warn(rust_2018_idioms)]

//! ...

use std::fmt::Debug;
use std::sync::{Arc, Mutex};

/// ...
pub fn pair<T>() -> (Verifier<T>, Caller<T>) {
    let calls = Arc::new(Mutex::new(Some(Vec::new())));

    let matcher = Verifier {
        calls: calls.clone(),
    };

    let spy = Caller { calls };

    (matcher, spy)
}

/// ...
#[derive(Debug)]
pub struct Caller<T> {
    calls: Arc<Mutex<Option<Vec<T>>>>,
}

impl<T> Caller<T> {
    /// ...
    pub fn call(&self, value: T) {
        let mut guard = self.calls.lock().unwrap();

        match guard.as_mut() {
            Some(calls) => calls.push(value),
            None => panic!("verify_call received a call after the verifier was consumed"),
        }
    }
}

/// ...
#[derive(Debug)]
pub struct Verifier<T> {
    calls: Arc<Mutex<Option<Vec<T>>>>,
}

impl<T> Verifier<T> {
    /// ...
    pub fn calls(self) -> Vec<T> {
        let mut guard = self.calls.lock().unwrap();
        guard.take().unwrap()
    }
}

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

    mod caller {
        use super::*;

        #[test]
        fn implements_traits() {
            use impls::impls;
            use std::fmt::Debug;

            // Given
            struct NotDebug;

            // Then
            assert!(impls!(Caller<i32>: Debug & Send & Sync & !Clone));
            assert!(impls!(Caller<NotDebug>: !Debug & Send & Sync & !Clone));
        }

        #[test]
        fn is_thread_safe() {
            // Given
            let (verifier, caller) = pair();
            let handle = std::thread::spawn(move || {
                caller.call(1);
            });

            // When
            handle.join().unwrap();
            let calls = verifier.calls();

            // Then
            assert_eq!(calls, &[1]);
        }

        #[test]
        #[should_panic(expected = "verify_call received a call after the verifier was consumed")]
        fn panics_when_called_after_verification() {
            // Given
            let (verifier, caller) = pair();
            let _calls = verifier.calls();

            // When
            caller.call(3);
        }
    }

    mod verifier {
        use super::*;

        #[test]
        fn implements_traits() {
            use impls::impls;
            use std::fmt::Debug;

            // Given
            struct NotDebug;

            // Then
            assert!(impls!(Verifier<i32>: Debug & Send & Sync & !Clone));
            assert!(impls!(Verifier<NotDebug>: !Debug & Send & Sync & !Clone));
        }

        #[test]
        fn initially_has_no_calls() {
            // Given
            let (verifier, _caller) = pair::<()>();

            // When
            let calls = verifier.calls();

            // Then
            assert_eq!(calls.len(), 0);
        }

        #[test]
        fn receives_calls_from_caller() {
            // Given
            let (verifier, caller) = pair();
            caller.call(1);
            caller.call(2);
            caller.call(3);

            // When
            let calls = verifier.calls();

            // Then
            assert_eq!(calls, &[1, 2, 3]);
        }
    }
}