Napoleon stopped Mark.

"Much as I appreciate it, don't defend me to your partner. She's right. What I read in the complaint didn't mesh with anything I know about you. If someone came up to Illya in front of me accusing him of something I knew that he didn't do, I wouldn't take it well either."

Whether that was his intention or not, Napoleon's answer got April wondering if this had actually been a test - to see if she would stand up for her partner the way he'd already stood up for her.