env-guard 0.1.0

Set and lock environment variables for tests
Documentation 
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# env-guard

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A process's environment is a form of global mutable state. In Rust, tests are run in a shared process. This means tests that modify environment variables can inadvertently affect each other. `env-guard` provides an interface to safely modify and lock the process environment, to prevent simultaneous access.

```rust
use env_guard::EnvGuard;
use std::env;

let var = "ENV_GUARD_TEST_VARIABLE";
assert!(env::var(var).is_err());

let guard = EnvGuard::lock([(var, Some("hello!"))]);
assert_eq!(env::var(var).unwrap(), "hello!");
drop(guard);

assert!(env::var(var).is_err());
```