Truth testing is a role of the ballot that says the judge should vote for the debater who proves the truth or falsity of the resolution. The aff burden is to prove the resolution true, and the neg burden is to prove the resolution false.
Truth testing is often combined with a philosophical framework to prove the resolution true or false. Since many resolutions have the word "ought," debaters can prove the truth or falsity of the resolution by proving there exists a moral obligation or prohibition upon doing the resolution. That is, if we have a moral obligation to do the resolution, then it is proven true that we ought to do the resolution, or vice-versa.
Truth testing is also commonly paired with tricks. Some tricks, like a prioris, function by proving that the resolution is inherently a true or false statement due to some logical or semantical property of the wording of the resolution. Other tricks, like moral skepticism, prove it is impossible to generate moral obligations, so the "ought" statement could never be proven true.
Here are some common justifications for truth testing.
Jurisdictional justifications for truth testing describe the way in which the judge determines the winner of the round. The judge only has the power to vote for the better debater because the ballot is specifically asking if the resolution is true or false in the given round which means the ballot is inherently asking for the truth or falsity of the resolution.
Inclusivity justifications usually talk about how truth testing is the most inclusive model because any offense can function under it. This inclusion argument is a hypothetical because only offense that is true can function under the model in reality.
Rule breaking justifications discuss the competitive aspects of debate as an activity in saying that other role of the ballots are self-serving because they break the rules of the game to "make it more interesting" whereas truth testing is a "rule" that puts debaters on a level field. Even if there are different ways to play a game, the winner is not determined off of those factors.
Definitional justifications provide some dictionary definitions for affirm and negate to show that they are related to the concept of truth.
Resolvability justifications portray truth and falsity as a binary system of evaluating arguments in the round which makes it the most resolvable. Other role of the ballots would fail in truth testing's stead because it leaves it up to the judge (and perhaps their personal biases) to resolve the round.
First, it is worth noting that you might not need to respond to truth testing. If you are reading a different philosophical framework that proves the resolution true or false, including utilitarianism, you could concede truth testing and argue that your framework proves the resolution true or false, too. However, if you opponent is leveraging truth testing to gain access to many tricks, it still might be worth contesting truth testing and going for an alternative role of the ballot, such as comparative worlds.
The most effective way to respond to truth testing, like any other role of the ballot, is to line-by-line the justifications and leverage your own role of the ballot.
Responses to Common Arguments
On Jurisdiction: Tab doesn't actually ask for the truth or falsity, but asks the judge whether they vote aff or neg which means it's not actually about the truth of the resolution. On Inclusivity: Truth testing is not the most inclusive because it excludes arguments that don't prove the truth or falsity of the resolution.
On Rule breaking: The person reading truth testing usually does it in a self-serving manner because they read it first and may also read a bunch of a prioris. That means that it still collapses to the idea that people only read role of the ballots to "make the game more interesting."
On Definitions: There are infinite definitions to pull from and several from each dictionary website which means there's no warrant in providing a definition.
On Resolvability: There may still be different conceptions of what is true and false. It may also be harder to resolve the round because you can't way between a claim of truth and a claim of falsity because they just clash.