For me, it was because I was checking for empty code before the flush. Flush should be executed 'before execution', so it has to be the first thing that happens.

given the name of the test, "preBufferedAbort", I assumed that the error comes from not calling flush on the output stream. however, adding that changes the error message to:

testpreBufferedAbort
program=''
Expected exception for unclean termination caught: java.lang.RuntimeException: Invalid empty program.
unclean termination expected:<1[]> but was:<1[2]>

Any hints on what magic is needed with this test case?

It's a label marking a location in the program for your flow control instructions to have targets.

I'm down to just a single test case erroring out for my java implementation of this kata:

testpreBufferedAbort
code=''
program=''
Expected exception for unclean termination caught: java.lang.RuntimeException: Invalid empty program.
unclean termination expected:<1> but was:

I'm puzzled. The "code" block is empty, yet there expects to be some output in the output stream? I dont understand how.

I'm at 114 of 115 passed, but I don't see how this test case can ever pass.