compiletest_rs 0.10.2

The compiletest utility from the Rust compiler as a standalone testing harness


This project is an attempt at extracting the compiletest utility from the Rust compiler.

The compiletest utility is useful for library and plugin developers, who want to include test programs that should fail to compile, issue warnings or otherwise produce compile-time output.

To use in your project

To use compiletest-rs in your application, add the following to Cargo.toml

compiletest_rs = "0.10.0"

By default, compiletest-rs should be able to run on both stable, beta and nightly channels of rust. We use the tester fork of Rust's builtin test crate, so that we don't have require nightly. If you are running nightly and want to use Rust's test crate directly, you need to have the rustc development libraries install (which you can get by running rustup component add rustc-dev --toolchain nightly). Once you have the rustc development libraries installed, you can use the rustc feature to make compiletest use them instead of the tester crate.

compiletest_rs = { version = "0.10.0", features = [ "rustc" ] }

Create a tests folder in the root folder of your project. Create a test file with something like the following:

extern crate compiletest_rs as compiletest;

use std::path::PathBuf;

fn run_mode(mode: &'static str) {
    let mut config = compiletest::Config::default();

    config.mode = mode.parse().expect("Invalid mode");
    config.src_base = PathBuf::from(format!("tests/{}", mode));
    config.link_deps(); // Populate config.target_rustcflags with dependencies on the path
    config.clean_rmeta(); // If your tests import the parent crate, this helps with E0464


fn compile_test() {

Each mode corresponds to a folder with the same name in the tests folder. That is for the compile-fail mode the test runner looks for the tests/compile-fail folder.

Adding flags to the Rust compiler is a matter of assigning the correct field in the config. The most common flag to populate is the target_rustcflags to include the link dependencies on the path.

// NOTE! This is the manual way of adding flags
config.target_rustcflags = Some("-L target/debug".to_string());

This is useful (and necessary) for library development. Note that other secondary library dependencies may have their build artifacts placed in different (non-obvious) locations and these locations must also be added.

For convenience, Config provides a link_deps() method that populates target_rustcflags with all the dependencies found in the PATH variable (which is OS specific). For most cases, it should be sufficient to do:

let mut config = compiletest::Config::default();

Note that link_deps() should not be used if any of the added paths contain spaces, as these are currently not handled correctly.


See the test-project folder for a complete working example using the compiletest-rs utility. Simply cd test-project and cargo test to see the tests run. The annotation syntax is documented in the rustc-guide.


  • The run-pass mode is strictly not necessary since it's baked right into Cargo, but I haven't bothered to take it out


Thank you for your interest in improving this utility! Please consider submitting your patch to the upstream source instead, as it will be incorporated into this repo in due time. Still, there are some supporting files that are specific to this repo, for example:

  • src/
  • src/
  • test-project/

If you are unsure, open a pull request anyway and we would be glad to help!