Having a test case like this [1], the executable model fails with:

"java.lang.AssertionError: [Message [id=1, kieBase=defaultKieBase, level=ERROR, path=r0.drl, line=-1, column=0
text=Unable to parse left part of expression: aBcde == "test"]]"

[1] https://gist.github.com/baldimir/7b4067d74d5fe32b0cb2360de14fd344