Env test util

Just a simple tool to manipulate environment variable in tests.

Usage

When initialising the variable manager with new, the actual content will be removed and stored in initial_value. You can then set a temporary value using the method with. The environment variable will then be reset to it's initial value when it will be dropped.

Examples

```rust use envtestutil::TempEnvVar;

std::env::setvar("MYVARIABLE", "ORIGINAL"); // set the variable to "ORIGINAL" let variable = TempEnvVar::new("MYVARIABLE"); // read the variable and stores it asserteq!(std::env::var("MYVARIABLE").ok(), None); let variable = variable.with("NEWCONTENT"); // set the environment variable with a new content asserteq!(std::env::var("MYVARIABLE").ok(), Some("NEWCONTENT".into())); drop(variable); asserteq!(std::env::var("MY_VARIABLE").ok(), Some("ORIGINAL".into())); ```

Don't forget to assign the variable in your tests, otherwise the drop function will be called right away

```rust use envtestutil::TempEnvVar;

std::env::setvar("MYVARIABLE", "ORIGINAL"); // set the variable to "ORIGINAL" TempEnvVar::new("MYVARIABLE").with("SOMETHINGELSE"); // read the variable and stores it asserteq!(std::env::var("MYVARIABLE").ok(), Some("ORIGINAL".into())); let variable = TempEnvVar::new("MYVARIABLE").with("SOMETHINGELSE"); // Instead, store it in a variable asserteq!(std::env::var("MYVARIABLE").ok(), Some("SOMETHINGELSE".into())); ```

Real life example

```rust

[test]

fn testingconntectiondatabase() { let originalurl = TempEnvVar::new("DATABASEURL").with("postgres://wrong-url"); let connection = Database::connect(); // something that reads the environment variable assert!(connection.iserr()); } ```