We present a critical review of 12 methods available today to emulate optical turbulence for the laboratory testing of astronomical adaptive optics systems, in particular, multiconjugate and extreme contrast modes. All published or known optical turbulence generation methods are presented, and their pros and cons are discussed, from static phase screens to fluid chambers. Optical turbulence measurement methods for the testing and characterization of turbulence generators are also reviewed. Results are summarized in a table with references at the end of the paper. The objective of this review is to provide a designer guide for optical turbulence generators.