>> Returns a `String` instead of a type which disallows the formulation of the problematic `assertEquals` to begin with.
> I'm not sure what the best attribution would be but "Make illegal states unrepresentable" would be a fantastic addition to this list pairing well with "parse, don't validate".
The phrases I have seen describing using types to make illegal states incapable of being represented are "programming with types"[0] and "type level programming"[1].