test_zip_lzma_compression_round_trips / test_default_zip_uses_deflate
built a real zip and read compress_type back off it — that only
reconfirms zipfile.ZipFile() honors its own compression= kwarg
(ZipExportSink's own tests already cover that forwarding). What this
command owns is resolving the --zip-compression string to the right
zipfile constant; assert that resolution directly against the mocked
ZipExportSink construction call instead. Drops the sample-doc copytree
setup those tests needed only to build a real archive.