After:
unlet! g:buffer
let g:ale_buffer_info = {}
Execute('ALE globals should be cleared when the buffer is deleted):
new
let g:ale_buffer_info = {
\ bufnr(''): {'temporary_file_list': [], 'temporary_directory_list': []},
\ 10347: {'temporary_file_list': [], 'temporary_directory_list': []},
\}
bdelete
AssertEqual {10347: {'temporary_file_list': [], 'temporary_directory_list': []}}, g:ale_buffer_info