Java 9 changed its character tables to unicode version 7.0. The table updates are listed here: http://hg.openjdk.java.net/jdk9/jdk9/jdk/rev/86206517258d
Because of this, character \u180E is no longer treated as whitespace, so TestUtil#randomWhitespace() fails.
I will remove this character from the list and update the documentation JRE_VERSION_MIGRATION.txt.
We should maybe make this character list dynamic (e.g. TestUtil initializes it on static class init one time by iterating over all 16 bit characters). Maybe somebody else has an idea (there is already a TODO in the code about that).