It might, depending on the child and circumstances. Anxiety/stress tends to increase tic'ing. Most individuals are able, by great mental effort, to suppress tics for short periods of time. High stakes performance situations (e.g., GATE testing) may increase anxiety in a setting (group testing) where tics are perceived as particularly detrimental to social status. For some, this can translate into diverting excessive mental energy to holding back tics, rather than, say, answering GATE testing items in a timely and accurate manner.
All the same considerations apply to OCD, especially any visible compulsions, and most of the other anxiety disorders. Stress increases the maladaptive symptoms of anxiety, and reduces effective use of coping strategies.
If you were to receive an accurate TS or anxiety disorder Dx, documentation, and access to a re-test with accommodations, you would probably want individual testing with a familiar test administrator, frequent breaks, and extended time.
