The assert_eq!() calls are calls to the assert equals macro: https://doc.rust-lang.org/std/macro.assert_eq!.html https://doc.rust-lang.org/std/macro.assert_eq!.

The assert_eq!() calls are calls to the assert equals macro: https://doc.rust-lang.org/std/macro.assert_eq!.html https://doc.rust-lang.org/std/macro.assert_eq!.html In rust macro functions look like functions but end in a bang(!), it's not using ! to mean negate. http://rustbyexample.com/macros.html http://rustbyexample.com/macros.html