"These tests [...] were “supposedly applicable to both white and black prospective voters who couldn’t prove a certain level of education” (typically up to the fifth grade). Yet they were “in actuality disproportionately administered to black voters.”
Additionally, many of the tests were rigged so that registrars could give potential voters an easy or a difficult version, and could score them differently as well. For example, the Veterans of the Civil Rights Movement describes a test administered in Alabama that is so entirely subjective that it measures the registrar’s shrewdness and cunning more than anything else."