Crate ephemeral_env 

A testing utility for creating ephemeral environments which are reset once they go out of scope.

Examples:

Once an EphemeralEnv drops out of scope, new env vars which were created whilst it was in scope will be dropped.

use ephemeral_env::EphemeralEnv;

assert!(std::env::var("MY_ENVIRONMENT_VARIABLE").is_err());
#[cfg(feature = "sync")]
{
    let mut ephemeral = EphemeralEnv::from_env_sync().unwrap();
    ephemeral.set_var("MY_ENVIRONMENT_VARIABLE", "test");
    assert_eq!(std::env::var("MY_ENVIRONMENT_VARIABLE").unwrap(), "test");
}
assert!(std::env::var("MY_ENVIRONMENT_VARIABLE").is_err());

Similarly, once an EphemeralEnv drops out of scope, modified env vars will revert to the value they held when the EphemeralEnv was created.

use ephemeral_env::EphemeralEnv;

unsafe {
    std::env::set_var("MY_ENVIRONMENT_VARIABLE", "Spanners! Shh!");
}
{
    let mut ephemeral = EphemeralEnv::from_env_sync().unwrap();
    ephemeral.set_var("MY_ENVIRONMENT_VARIABLE", "test");
    assert_eq!(std::env::var("MY_ENVIRONMENT_VARIABLE").unwrap(), "test");
}
assert_eq!(std::env::var("MY_ENVIRONMENT_VARIABLE").unwrap(), "Spanners! Shh!");

Async interface

If you’re testing across await points then it’s inadvisable to use EphemeralEnv::from_env_sync(), as this will use a std::sync::Mutex, which isn’t Send.

Instead, ephemeral_env provides [from_env_async()], which will use Tokio’s async-compatible Mutex instead:

use ephemeral_env::EphemeralEnv;

assert!(std::env::var("MY_ENVIRONMENT_VARIABLE").is_err());
{
    let mut ephemeral = EphemeralEnv::from_env_async().unwrap();
    ephemeral.set_var("MY_ENVIRONMENT_VARIABLE", "test");
    // Without the async interface, this call would cause a warning to be shown, and there
    // would be a potential for the mutex held by the ephemeral environment to block the
    // event loop.
    tokio::time::sleep(Duration::from_millis(500)).await;
    assert_eq!(std::env::var("MY_ENVIRONMENT_VARIABLE").unwrap(), "test");
}
assert!(std::env::var("MY_ENVIRONMENT_VARIABLE").is_err());

Structs

EphemeralEnv