public/rust/tests/handling_test/src/main.rs

use std::fs::{File, OpenOptions};
use std::io::prelude::*;
use std::io::{ErrorKind, Write};
use handling::*;

fn main() {
    let path = "a.txt";
    File::create(path).unwrap();
    open_or_create(path, "content to be written");

    let mut file = File::open(path).unwrap();

    let mut s = String::new();
    file.read_to_string(&mut s).unwrap();
    println!("{}", s);
    // output: content to be written
}

#[cfg(test)]
mod tests {
	use super::*;
	use std::fs;
	use std::panic;

	fn get_file_content(filename: &str) -> String {
		let mut file = File::open(filename).unwrap();
		let mut s = String::new();
		file.read_to_string(&mut s).unwrap();
		fs::remove_file(filename).unwrap();
		return s;
	}

	#[test]
	fn test_if_file_exists() {
		let filename = "test_existing_file.txt";
		let content = "hello world!";
		File::create(filename).unwrap();
		open_or_create(filename, content);

		assert_eq!(content, get_file_content(filename));
	}

	#[test]
	fn test_create_file() {
		let file = "no_existing_file.txt";
		let content = "hello world!";
		open_or_create(file, content);

		assert_eq!(content, get_file_content(file));
	}
	#[test]
	fn test_error_case() {
		let filename = "hello.txt";
		File::create(filename).unwrap();
		let mut perms = fs::metadata(filename).unwrap().permissions();
		perms.set_readonly(true);
		fs::set_permissions(filename, perms).unwrap();

		let result = panic::catch_unwind(|| open_or_create(filename, "test"));
		fs::remove_file(filename).unwrap();
		assert!(result.is_err());
	}
}