Hello Joel,
The CEM Test is not predictable in the same way as, for example, the GL Test and therefore preparing for it will necessitate practising a wide range of core skills across the examined subjects.
There is no published syllabus. I think that you will find that most teachers/tutors, like myself, will create their own scheme of work – perhaps basing it on Key Stage 2 maths + English and then adding in NVR and VR specific skills, along with some methods of extending vocabulary knowledge and increasing mental arithmetic speed.