Yes, that's the idea. The literacy test isn't hard, it's impossible by design. Several of the questions are paradoxes, allowing the voter registrar to pick the other solution or disqualify them for using more than one answer. And you have to do all thirty questions in ten minutes.
This is where the term "grandfather clause" comes from: the excuse being that we need to have educated, informed voters, but if your grandfather was educated enough to vote then clearly so were you. The grandfathers of black people being slaves or children of slaves, they where oh-so-coincidentally exempt from this.
There was another way of doing it that even managed to dodge the grandfather clause though, which was recitation tests. They'd give everybody parts of the state or US Constitution, and tell them to recite it. The registrar would judge if it had been recited correctly, and if it had, you could vote. Of course, the registrar also chose the excerpt used, and so white people would get a single sentence and black people would get a legalese-ridden paragraph and then be disqualified for their accent even if they made it through.
I've also heard tales along the lines of the "literacy" test being to recite the entire US Constitution from memory, which then ran into problems when one determined fellow actually did it.
So if you ever wonder why I get rather pointed when people start talking about the idea of a voter competency test, this is why.