In Taiwan, the proficiency test is TOCFL. I'm not sure what your current level of Chinese is but there are 3 levels: Beginners (A), Intermediate (B) and Advanced (C). To make things a bit complicated, each level is split into two so A is Level 1 & 2, B is Level 3 & 4 etc. The higher the number, the harder the material, however you would only really notice it (especially in reading and listening) by the text or dialogue being longer.
The listening and reading is in one (computer) test, speaking and writing are both separate.
TOCFL is all in traditional characters.
In mainland China, Hong Kong and various places internationally, it is HSK. There are 6 levels (6 being the highest). HSK combines reading, writing and listening all in one paper. Speaking is a separate exam. I did HSK in Hong Kong and it was a paper exam, however in the mainland, it was computer based.
The difference in my opinion is that grading wise, HSK gives you an overall grade i.e if you are really good in reading and writing but was a bit poor in listening, the shortfall could even it self out. (For higher levels, the pass rate is 180 out of 300) However, in TOCFL, you need to pass each level separately to determine your overall grade (e.g You may of passed Level 4 reading but your listening was Level 3, so subsequently your overall grade is Level 3.)
HSK is also in simple characters. The content is also a bit different.
I found HSK more grounded in practical situations whereas TOCFL can throw in some obscure sayings which you may or may not of learned in the classroom.I personally found TOCFL harder, as the grading system is quite stressful.
If I can be a bit controversial, I am not sure if TOCFL is recognised internationally (the whole is Taiwan a country issue), therefore I purposely took HSK as if I return home (UK), I know employers dealing with China / Chinese language will have heard of it.
Hope this helps.