Programming Ruby 3.3: Extraneous "rb" in text

Title: Name of book: Programming Ruby 3.3 (page 227)

On page 227 there’s a section entitled RSpec and Mocks.

Immediately following the heading is the following text, edited for length:

rb In addition to minitest, RSpec also allows you...

The “rb” above appears to be an extraneous bit of text that was accidentally included.