Avoiding putting simple one-file modules in their own folder.
Usual Rust practice is to put tests in the same file they are testing. I don't see any magic in the texttests that would require tests and code to be in separate files, but I am not entirely sure, so I added the risky tag.
`Vec` and `String` are in the prelude, so qualifying them with `vec::Vec` and `string::String` is unnecessary.
Standard Rust formatting practice