Pseudo

A small mocking library for Rust.

Documentation

Pseudo lets you mock Trait implementations so that you can track function call arguments and set return values or overrides functions at test time.

Here's a quick example:

extern crate pseudo;

use pseudo::Mock;

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

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

impl Foo for MockFoo {
    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
}

#[test]
fn doubles_return_value() {
    let mock = MockFoo { expensive_fn: Mock::default() };

    mock.expensive_fn.return_value(1000);

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

#[test]
fn uses_correct_args() {
    let mock = MockFoo { expensive_fn: Mock::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)));
}

More examples are available in the examples directory.