There's definitely a line, and according to the tests it doesn't matter how feint the line is, it's a negative. Apparently you should test with your first urination of the day because it gives you an idea of the worst-case scenario.

I'm pretty much in the same situation as you (9 days now with a test in the next few days) so for your sake and mine I hope and believe you're good. Couldn't hurt to dilute some...