What does QET test?

I've seen a lot of conflicting information about the QET format. Some people say we have to write two essays, while others say we need to read two passages and write one essay. I've also heard that we'll only read one passage and then write a 300–400-word essay based on it.

Could anyone clarify which format is correct? If the last one is true, how are we expected to write a well-developed argumentative synthesis essay using only one source?