I advice either monkeytype or keybr, both have a setting for code

Honestly, I'd recommend using the good ol' gtypist.

It uses mostly real (or contrived) segments of text, which appear as if they were taken out of newspapers or personal letters. It has both beginner and advanced sets of text, and a whole community of custom texts that you can use. I've personally learned touch typing from scratch by using this program alone.

Monkeytype.com has many "code" dictionaries to choose from.