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Part of me wants to respond sarcastically to this but I’ll restrain myself.
The CFA Institute sets the curriculum and the exam; the mock exam provided by them is the closest substitute you can get to the actual exam and is invaluable. Moreover, Schweser’s mock exams have been described as a bit weak in one aspect on these forums.
Still, it is better to do all four mock exams, starting with the CFA Institute one, and carefully working through your incorrect answers following each exam.