It's possible. It was designed to be. It was used because southern Blacks actually did have a lower literacy rate than Whites at the time and this was seen as the most expedient "filter" they could create.
The real racism was in all the ways to bypass the test. Grandfather clauses, land ownership clauses, "demonstrated understanding" options. Most White people challenged by the test wouldn't ever need to actually confront it.
These weren't the only requirements either. You had to be of "good character" and "understand the duties and obligations of citizenship under a republican form of government" and to be able to "read _and_ write."
Finally even if you were Black and managed all of this it wasn't at all a guarantee that your registration or vote would be accepted. Sometimes this understanding would be communicated in an act of violence.
The test is a tiny archival curiosity created by a much more overt system.
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