There are probably no known "neutral" examples of this. I'm basing this on the fact that proponents of such systems (sometimes called epistocracy) don't bring any (good) examples of prior actual voting tests. They propose they these tests should be like citizenship tests etc., e.g. Jason Brennan writes:
Or, an epistocracy might allow every citizen to vote at the same time as requiring them to take a test of basic political knowledge and submit their demographic information. With such data, any statistician could calculate the public’s ‘enlightened preferences’, that is, what a demographically identical voting population would support if only it were better informed. An epistocracy might then instantiate the public’s enlightened preferences rather than their actual, unenlightened preferences.
A major question is what counts (and who decides what counts) as political competence, or basic political knowledge. We don’t want self-interested politicians rigging a political competence exam in their own favour. One might use widely accepted pre-existing tests; the Unites States citizenship test, for example, or the same questions that the American National Election Studies have used for 60 years. These questions – who is the current president? Which item is the largest part of the federal budget? – are easily verifiable and uncontroversial, plus an ability to answer them correctly is strongly correlated with the kind of political knowledge that does matter in an election. [...]
On the other hand, it’s true (at least right now) that certain demographic groups (such as rich white men) are more likely to pass a basic political knowledge test than others (such as poor black women). Hence the worry that epistocracies will favour the interests of some groups over others. But this worry might be overstated. Political scientists routinely find that so long as individual voters have a low chance of being decisive, they vote for what they perceive to be the common good rather than their self-interest. Further, it might well be that excluding or reducing the power of the least knowledgeable 75 per cent of white people produces better results for poor black women than democracy does.
On the other hand you could look at some sample "literacy tests" that were used as actual voting disenfranchisement tools in the American South.
As bit of an aside, criticism of Brennan's proposal:
If epistocracy is defined as a system where only informed people can vote, you must first define what an informed person is, and there’s no clear way to do that. In the Times op-ed, Brennan suggests—almost as an aside—that the American citizenship test could be used to determine one’s competence. But the civics questions on the citizenship test aren’t much more than basic facts about the U.S. government: the number of senators, the function of the Supreme Court, the names of the branches of government. If you know all three answers to the last question, congratulations—you’re among the quarter of Americans who can do so, which suggests that this definition of competence would disenfranchise a lot of people. More to the point, knowing these doesn’t make you a more informed voter. Using a citizenship test to determine if someone is an informed voter is like judging their ability to drive a car based on how well they can identify makes and models. [...]
There’s historical precedent for this kind of disguised discrimination in the form of poll taxes and literacy tests. These were principally meant to outsmart the Fifteenth Amendment and disenfranchise Black voters after the Civil War, although they were a barrier to poor white voters as well, even with grandfather clauses. While poll taxes and literacy tests didn’t quite create an aristocracy or a meritocracy, but they created class-based systems in which the lowest classes—the least wealthy or the least educated—were stripped of the right to vote. Epistocracy would have a similar effect by becoming another barrier to these voters.
Voter ID laws, poll taxes and literacy tests were all employed by state legislatures that consisted predominantly (if not exclusively) of white men, and this underscores what is perhaps the fundamental flaw of an epistocratic system: Whoever gets to define what an informed voter is will have the power to shape the electorate. We see the same thing happening with redistricting and gerrymandering; the bodies that draw legislative districts are able to consolidate the opposing party’s voters in one district or scatter them across multiple districts, diminishing their impact. What’s to say that a body in charge of determining who’s informed enough to vote won’t similarly try to hinder the opposing party by declaring its voters too uninformed to vote?