Set environment variables temporarily.

This crate is useful for testing with different environment variables that should not interfere.

This code started as a small test helper written by @fabian-braun and @nbaztec and published by @fabian-braun on StackOverflow. @vmx found it useful and took the time to make it a proper crate.

temp_env::with_var("MY_ENV_VAR", Some("production"), || {
    // Run some code where `MY_ENV_VAR` set to `"production"`.
});


temp_env::with_vars(
    vec![
        ("FIRST_VAR", Some("Hello")),
        ("SECOND_VAR", Some("World!")),
    ],
    || {
        // Run some code where `FIRST_VAR` is set to `"Hello"` and `SECOND_VAR` is set to
        // `"World!"`.
    }
);

temp_env::with_vars(
    vec![
        ("FIRST_VAR", Some("Hello")),
        ("SECOND_VAR", None),
    ],
    || {
        // Run some code where `FIRST_VAR` is set to `"Hello"` and `SECOND_VAR` is unset (even if
        // it was set before)
    }
);

This crate sets and unsets environment variables for the currently running (Rust) process. It leverages std::env::set_var.

The provided functions temp_env::with_* provide the following features:

• Avoid interference when running concurrently
• Reset previously set env variables back to their original value upon completion, also in case of panic
• Temporarily unsetting env variables

Note that the crate makes use of a singleton mutex to avoid side effects between concurrently running tests. This may impact the degree of concurrency in your test execution.

This project is licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE) or https://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or https://opensource.org/licenses/MIT)

at your option.