docs: add env_test example

Author: codinaut

examples/env_test.rs

@@ -0,0 +1,33 @@
+use std::env;
+use std::ffi::OsString;
+
+fn main() {
+    println!("Name: {}", get_name().to_str().unwrap());
+}
+
+fn get_name() -> OsString {
+    match env::var_os("NAME") {
+        Some(value) => value,
+        None => OsString::from("default-value"),
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use envtestkit::lock::{lock_read, lock_test};
+    use envtestkit::set_env;
+
+    #[test]
+    fn get_name_default() {
+        let _lock = lock_read();
+        assert_eq!(get_name(), "default-value")
+    }
+
+    #[test]
+    fn get_name_overriden() {
+        let _lock = lock_test();
+        let _test = set_env(OsString::from("NAME"), "not-default-one");
+        assert_eq!(get_name(), "not-default-one")
+    }
+}