type TestResult = Result<(), Box<dyn std::error::Error>>;
#[test]
fn write_read_file_exists() -> TestResult {
let fs = crate::filesystem::temp()?;
let pathbuf = fs.write_file("foo", "content")?;
let c = fs.read_file("foo")?;
assert_eq!(c, "content");
assert!(fs.file_exists(&pathbuf));
Ok(())
}