Pseudo

A small mocking library for Rust.

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.

Can't mock a Send Trait

Pseudo cannot mock a trait that is Send. Example:

    fn send() {
        pub trait A {
            fn foo(&self);
        }

        struct MockA {
            foo: Mock<(), ()>
        }
        impl A for MockA {
            fn foo(&self) {
                self.foo.call(())
            }
        }

        let mock = MockA{foo: Mock::default()};
        let _ = Box::new(mock) as Box<A + Send>;
    }

gives the following error:

error[E0277]: `(dyn std::ops::Fn(()) + 'static)` cannot be shared between threads safely
   --> src/t_pseudo.rs:431:17
    |
431 |         let _ = Box::new(mock) as Box<A + Send>;
    |                 ^^^^^^^^^^^^^^ `(dyn std::ops::Fn(()) + 'static)` cannot be shared between threads safely                                                   
    |
    = help: the trait `std::marker::Sync` is not implemented for `(dyn std::ops::Fn(()) + 'static)`
    = note: required because of the requirements on the impl of `std::marker::Sync` for `std::ptr::Unique<(dyn std::ops::Fn(()) + 'static)>`
    = note: required because it appears within the type `std::boxed::Box<(dyn std::ops::Fn(()) + 'static)>`
    = note: required because it appears within the type `std::option::Option<std::boxed::Box<(dyn std::ops::Fn(()) + 'static)>>`
    = note: required because of the requirements on the impl of `std::marker::Sync` for `std::sync::RwLock<std::option::Option<std::boxed::Box<(dyn std::ops::Fn(()) + 'static)>>>`
    = note: required because of the requirements on the impl of `std::marker::Send` for `std::sync::Arc<std::sync::RwLock<std::option::Option<std::boxed::Box<(dyn std::ops::Fn(()) + 'static)>>>>`
    = note: required because it appears within the type `pseudo::Mock<(), ()>`
    = note: required because it appears within the type `<t_pseudo::t::Pseudo as TestSuite>::send::MockA`
    = note: required for the cast to the object type `dyn <t_pseudo::t::Pseudo as TestSuite>::send::A + std::marker::Send`

iredelmeier / pseudo Goto Github PK

pseudo's Introduction

Pseudo

A small mocking library for Rust.

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pseudo's Issues

Can't mock a Send Trait

Feature Request: Sequential Returns

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