Crate double

Double is a fully-featured mocking library for mocking Trait implementations.

The Double struct tracks function call arguments and specifies return values or function overrides.

This library is based off iredelmeier's initial mocking implementation. Massive thanks to her implementation for inpsiring me to work on this. Her repo can be found here:

https://github.com/iredelmeier/pseudo

If you're interested in testing, check out her other repositories too!

Examples

use double::Double;

trait Foo: Clone {
    fn expensive_fn(&self, x: i64, y: i64) -> i64;
}

#[derive(Clone)]
struct DoubleFoo {
    pub expensive_fn: Double<(i64, i64), i64>,
}

impl Foo for DoubleFoo {
    fn expensive_fn(&self, x: i64, y: i64) -> i64 {
        self.expensive_fn.call((x + 10, y))
    }
}

fn double_expensive_fn<T: Foo>(foo: &T, x: i64, y: i64) -> i64 {
    foo.expensive_fn(x, y) * 2
}

fn test_doubles_return_value() {
    let mock = DoubleFoo { expensive_fn: Double::default() };

    mock.expensive_fn.return_value(1000);

    assert_eq!(double_expensive_fn(&mock, 1, 2), 2000);
}

fn test_uses_correct_args() {
    let mock = DoubleFoo { expensive_fn: Double::default() };

    assert!(!mock.expensive_fn.called());

    double_expensive_fn(&mock, 1, 2);

    assert_eq!(mock.expensive_fn.num_calls(), 1);
    assert!(mock.expensive_fn.called_with((11, 2)));
}

test_doubles_return_value();
test_uses_correct_args();

Structs

Mock	Used for tracking function call arguments and specifying a predetermined return value or mock function.

Type Definitions

Double