Second, I didn't give you an example. You asked where it said in the Constitution such acts were valid. I pointed it out chapter and verse. No "example" was involved. Just the plain words and meaning of the Constitution.
Third, the pertinent language in the Constitution has been overridden by the Voting Rights Act. This was made possible by the Fourteenth Amendment, which qualifies that such literacy tests may not be constructed in such a way as to deny the Equal Protection of the law. So, clearly such tests were no longer Constitutional after July 9th 1868, IF they had an impact in their application which denied a particular identifiable group of Americans the Equal Protection of Law. Once again, you've asked a silly question, and once again you are answered. I highly advise you to read the Constitution, so you aren't angered by your own ignorance of it next time.
Finally, the Slate article is an example of liberal hysteria, and of course you fell right into it.
Nobody is talking about bringing literacy tests back in order to qualify electors, and that is NOT what the VRA decision by the Supreme Court will do.[That section of the VRA is not even affected by the decision.] The US DOJ has brought cases against numerous Southern States, denying them the right to require voter ID: under ONE section of the VRA Southern States cannot change their voting laws without prior Federal approval. This meant that Republicans in Southern States would continue to have their votes diluted by fraudulent Democrat practices, and there was nothing they could do about it, because the DOJ would simply deny those states the ability to correct these abuses. In effect, the US Department of "Justice" was using the VRA to deny southerners the Equal Protection of law by way of the Voting Rights Act. This is EXACTLY the opposite of what the VRA was intended to accomplish, and what the SCOTUS has struck down. Good riddance.
When someone insults me with a typo and interpretations of the Constitution while not understanding that two brilliant people can interpret the document in different ways, no matter how many words they type will not impress me all that much.