De gedragstest toont of de hond blaft.

Dutch usually writes compound nouns as a single word. So gedragstest is made from:

• gedrag = behavior
• test = test

Together they form gedragstest = behavior test.

This is very normal in Dutch. English often uses spaces where Dutch prefers one compound word.

Because test is a de-word, and in Dutch compounds the last part usually determines the article.

So:

• de test
• therefore de gedragstest

The same applies to de hond: hond is also a de-word.

Toont is the present tense of tonen, which means to show.

So:

• ik toon = I show
• jij toont
• hij/zij/het toont
• de gedragstest toont = the behavior test shows

In this sentence, toont is a bit formal or written-sounding. In everyday Dutch, people often say laat zien instead.

Not here. In this sentence, of means whether.

Dutch of can mean two different things:

• or
  
  • Koffie of thee? = Coffee or tea?
• whether / if in an indirect yes-no question
  
  • Ik weet niet of de hond blaft. = I don’t know whether the dog barks.

So in De gedragstest toont of de hond blaft, of introduces the idea whether the dog barks.

Because this is whether, not a condition.

Use of for whether:

• Ik weet niet of de hond blaft.
• De gedragstest toont of de hond blaft.

Use als for a condition, like if/when:

• Als de hond blaft, word ik wakker. = If the dog barks, I wake up.

A good shortcut is:

• of = whether
• als = if in conditional sentences

They do. This clause already has the verb at the end.

In of de hond blaft:

• de hond = subject
• blaft = verb

Since there are no other elements, the verb is simply last already.

You can see the rule more clearly if you add another word:

• main clause: De hond blaft vaak.
• subordinate clause: ... of de hond vaak blaft.

So after of, Dutch uses subordinate-clause word order.

The infinitive is blaffen = to bark.

For the present tense:

• stem: blaf
• ik blaf
• jij/de hond/hij/zij blaft

So de hond blaft is the normal third-person singular form.

The -t is added because the subject is de hond = it/he.
There is only one t, not two.

Yes, it is grammatical and understandable. But toont sounds a little formal.

A more everyday version would often be:

• De gedragstest laat zien of de hond blaft.

Both are correct. The difference is mainly style:

• toont = a bit more formal/written
• laat zien = more common in everyday speech

De hond means the dog, so it refers to a specific dog that is known from the context.

If you said een hond, that would mean a dog, more general or unspecified:

• De gedragstest toont of de hond blaft. = about a particular dog
• De gedragstest toont of een hond blaft. = about some dog, not a specific one

In practice, de hond is the more natural choice if a specific dog is being tested.