def METHOD_NAME(source, target, old_docs, new_docs):
    builder = CopyBuilder(source, target, delete_orphans=True)
    source.update(old_docs)
    source.update(new_docs)
    chunk_queries = list(builder.prechunk(2))
    assert len(chunk_queries) == 2
    assert chunk_queries[0] == {"query": {"k": {"$in": [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]}}}