header-only: output=0 finished=false needsInput=true remaining=0
exact: output=HELLO finished=true needsInput=true remaining=0
truncated: output=HELLO finished=false needsInput=true remaining=0
with-tail: output=HELLO finished=true needsInput=false remaining=4 tail=NEXT
matrix: 3 output sizes x 5 tail lengths checked
PASS 53 checks; one zlib stream, no files or network I/O
