Hani, in his usual unusual style (a warning to sensitive souls), points out a common unit test error:
So after a few days of pointlessly scrolling around, I find the culprit. It's at this point that I completely lose it and start laughing hysterically. I can't quite believe the test I'm looking at.
The test for http state works thusly: It gets at the class that holds the map. It uses reflection to access the (private) map, makes it accessible, and manually puts a value in it. Having done so, it then calls a method which basically just reads from the map, and then compares the two.
It's mind boggling to me that someone would write such a complex and awkward test to basically test that HashMap functions as a....map.
Simple solution: don't do this. There are several technical approaches superior to all the reflection described, but just don't bother to unit test the JDK.