assert_eq!(format!("{:.1000e}", 1), format!("1.{}e0", "0".repeat(1000)));
//test zero precision
assert_eq!(format!("{:.0e}", 1), format!("1e0",));
+ assert_eq!(format!("{:.0e}", 25), format!("3e1",));
//test padding with precision (and sign)
assert_eq!(format!("{:+10.3e}", 1), " +1.000e0");