Real sentences with the punctuation left in — commas, semicolons, colons, quotation marks, apostrophes, dashes, brackets and question marks. Most typing tests strip these out. Most writing does not.
Punctuation keys are on the edges of the keyboard, assigned to the weakest fingers, and half of them need the shift key. A comma is easy; a semicolon is the right pinky; a colon is the same key shifted; a question mark is a shifted slash under the pinky again; opening quotation marks need shift and the pinky and are followed immediately by a capital letter, which needs shift on the other hand. Sentence-level punctuation is a run of pinky and shift work that ordinary tests, built from lowercase words, never measure.
The text here is prose with its punctuation intact, plus a share of the dense constructions — dialogue with quotation marks, parenthetical asides, lists with semicolons, hyphenated compounds — that appear in real writing.
A drop of ten to fifteen per cent from your plain-prose speed is typical. If the drop is larger, the shift key is usually the reason: many typists shift with the same hand as the letter, which twists the hand and costs a fraction of a second every time. The rule is to shift with the opposite hand — right pinky on shift for a capital A, left pinky for a capital L — and the coach will flag the capitals as hesitations if you are not doing that.
Rhythm matters here more than on any other test. Punctuation is where fluent typists pause; the rhythm score tells you whether the pause is a natural sentence break or a hunt for the key.
The apostrophe is the most common punctuation mark in English after the comma and full stop, and it is the right pinky reaching sideways. Quotation marks are the same key shifted. Dashes are the top-right corner. Practising these three alone — the Symbols course has a lesson for exactly them — usually recovers most of the gap between prose speed and punctuated-prose speed.
Writers and editors, obviously. Legal and academic typists, whose sentences are the most heavily punctuated in the language. Transcriptionists, who must reproduce every mark. And programmers, for whom punctuation is not decoration but syntax — the code tests take that further with brackets and operators.