Every applicant must take an online assessment (basically a math test) before being allowed to interview -- even if you're not going to be developing software, etc. EVERYONE takes it. It's online, then you take a written one in the office to ensure you didn't cheat. It's archaic and doesn't fit everyone's potential job roles.
Interviews are often scheduled last minute, so you may not have the actual manager you'll be working under interview you -- oftentimes it's just another employee who was told at the last second. You'll also interview with the CEO and potentially the CFO if they're in the office.