test_double

A procedural macro that can swap in mock objects, dummy objects, or other test doubles only when testing. Requires Nightly Rust.

There are many limitations at present:

• Does not support grouped imports, like use blah::{foo, bar};
• Does not support nested paths, like use blah::{*, something::{foo, bar}};
• The substituted type can't be changed when using the function-like macro

To use, add the following to your Cargo.toml:

[dependencies]
test_double = "0.1.1"

Note that this crate has not yet reached version 1.0, so the API may change drastically between releases.

Substituting One Type

The substituted name defaults to the original name, postfixed with "Mock":

#[test_double]
use ::image::ImageManager;

// Expands to:

#[cfg(not(test))]
use ::image::ImageManager;
#[cfg(test)]
use ::image::ImageManagerMock as ImageManager;

If you'd like to change the subsituted name, you can do so:

#[test_double(IMDummy)]
use ::image::ImageManager;

// Expands to:

#[cfg(not(test))]
use ::image::ImageManager;
#[cfg(test)]
use ::image::IMDummy as ImageManager;

Substituting Multiple Types

If you'd like to substitute multiple types at once, you can use the function-like macro. Note that this does not support changing the substituted name yet.

test_doubles! {
    use ::image::ImageManager;
    use ::texture::TextureManager;
}

// Expands to:

#[cfg(not(test))]
use ::image::ImageManager;
#[cfg(test)]
use ::image::ImageManagerMock as ImageManager;
#[cfg(not(test))]
use ::texture::TextureManager;
#[cfg(test)]
use ::texture::TextureManagerMock as TextureManager;