Crate mock_me

MockMe is a tool used to mock dependencies / function calls when running unit (lib) tests in Rust.

How to Use

Simply use the macro as seen in the example below. When this code is run normally, MockMe will have no effect. However, when the code is run as part of a unit test #[cfg(test)], the mocked token will be used instead.

In order to use, we first must mark the functions that we would like to mock. When running tests, we then identify the replacement function that we would like to inject.

#![feature(proc_macro)]
extern crate mock_me;
use mock_me::{mock, inject};

// Below we will create two mocking identifiers called id_1 and id_2.
// We will then provide the name of the two functions we are mocking, as well as
// their type signature. In future iterations, hopefully the signature won't be needed.
#[mock(id_1="external_db_call: fn(u32) -> String", id_2="other_call: fn() -> String")]
fn my_super_cool_function() -> String {
    let input = 42u32;
    // external_db_call will be replaced with fake_mocked_call during testing
    let db_result = external_db_call(input);

    // other_call will also be replaced
    let other_result = other_call();
    format!("I have two results! {} and {}", db_result, other_result)
}

// Finally, when we run our tests, we simply need to provide the identifier we previously used,
// as well as the name of the replacement function
#[test]
#[inject(id_1="db_fake", id_2="other_fake")]
fn actual_test2() {
    let result = my_super_cool_function();
    assert_eq!(result, "I have two results! Faker! and This is indeed a disturbing universe.");
}

fn db_fake(_: u32) -> String { "Faker!".to_string() }
fn other_fake() -> String { "This is indeed a disturbing universe.".to_string() }

Functions

inject	The inject macro is used to replace a mocked function with an alternative implementation. Its signature contains the identifier that is being mocked, with the function that will replace the mocked function within quotes.
mock	The mock macro is used mock a concrete function that is not desired during unit tests. Its signature contains the identifier that is being mocked, with the function that will replace the mocked function within quotes, as well as the mocked function signature.