Beijing China Conservatory of Music has music examinations for traditional Chinese music instruments for grade 1 to Diploma.
Each grade has its own practise passages as well as classic tunes that is representative of the grade.
The music scores for grades 1-6 and grades 7-Diploma are contained in 2 separate books.
If you want a comprehensive collection of solo pieces for traditional Chinese instruments from easy to advanced, the Central Conservatory of Music grading book of scores are the books to get.
Available for pipa, erhu, dizi, zhongruan and guzheng.