There are plenty of resources out there that allow us as learners to check our progress and give us goals to work towards. I don’t know of any official credentials that can be earned through online testing, but I do recommend all of these:
Clavis Sinica Chinese Character Quiz–based off of characters and their English translations in 4 skill levels. Estimates the number of characters that you know.
Good: Wide variety of characters, relatively randomized, can save your scoreBad: Can’t skip Easy/Basic Characters, some poorly translated answers
The Clavis Sinica Character Test is also available on mobile:
MGDB Chinese Character Quiz–Similar to above quiz, but does not estimate number of characters known. Gives you a list of missed characters once complete.
Good: Time (counts up), provides list of missed characters, can customize lists like flashcards
Bad: No mobile app
Online Diagnostic Assessment developed for linguistic trainees at the Defense Language Institute. The test uses answers from early questions to choose later questions. The test will give you an unofficial score of your level on a scale of 1 to 5 as used by the Interagency Language Roundtable and is supposed to be a decent indicator of performance on the Defense Language Proficiency Test.
Opinion: The tests seemed to accurately assess my level, but taking it more than once I found that some of the passages turned up each time, so it doesn’t seem that there is a big database. It’s also unfortunate that you can not review the questions you’ve missed.
Note: Some passages in Simplified, some Traditional, you can’t choose.
Chinese Reading World (University of Iowa)— Once you get into the Beginner, Intermediate, or Advanced readings page, navigate to the bottom of the page and you will see the set of 5 assessments for the level. Each test is broken up into word comprehension/synonym recognition and multiple choice questions on various passages.
Opinion: It’s nice that you can see your score afterwords, but unfortunately I don’t think there is a way to review the questions you missed here. A good resource nonetheless.
This resource was also one of my favorites for reading practice.
Past HSK Test Papers–Hanban has started posting the full versions of previously administered HSK tests, to cover reading (inc. grammar and word usage), writing, and listening. While there is no real way to score your own writing, the answers for the reading and listening sections of the test are both provided for reference. Great practice if you are looking to take the actual test, still worthwhile if not.