I've been reading "Autumn in the Heavenly Kingdom," the story of a man who failed the Chinese SAT's and decided to be a Christian, Chinese version of L. Ron Hubbard mixed with ISIS. They keep bringing up these exams and I can't stop wondering what was on these exams and what it was like to take them. Do we have copies? How hard was it really?
Two things I want to note in regards to the answer given by /u/xingfenzhen.
One. The Qing undertook a major reform of the civil service exams in 1901 and changed the structure significantly. Therefore, the final exam that was held in 1904 is not that good of a representation of what candidates were tested on during Hong Xiuquan's era. The Qing test structure for the palace examinations established in 1787, which would be much closer to what Hong Xiuquan's generation was tested on, are as follows:
Stage one: Three essays on the Four Books (The Great Learning, the Doctrine of the Mean, The Analects, and Mencius.) and one Five Character Eight Rhyme Poem.
Stage two: Five essays on the Five Classics (Classic of Poetry, Book of Documents, Book of Rites, Book of Changes, and the Spring and Autumn Annals).
Stage three: Five questions on history and current policies.
As you can see, the pre-1901 exams placed much more emphasis on Confucian classics. A passage from one of the books will be provided for analysis, and the essay will be judged not only for its content (how well you understood the classics) but also for prose, penmanship, and adherence to structure. See my own explanation of the Eight-Legged Essay - as well as penmanship.
Two. Hong Xiuquan failed the county-level examinations, the lowest tier and arguably the easiest of the exams. The questions that are available today are almost all for the metropolitan or palace examinations, making them considerably more difficult.
This answer (https://www.reddit.com/r/AskHistorians/comments/2nrv12/what_was_the_actual_content_of_chinese_civil/cptethd/) by /u/xingfenzhen has an english translation of the last civil service exam.
Here you have some good answers specifically about how hard they were, by /u/WafflesDev and /u/Tiako
tl;dr: They were really fucking hard.