Before:
  Save g:ale_buffer_info
  Save g:ale_disable_lsp

  let g:ale_disable_lsp = 0
  unlet! b:ale_disable_lsp

  function! CreateError(type, message) abort
    let l:diagnostics = []

    if !empty(a:message)
      let l:diagnostics = [{
      \ 'start': {'line': 1, 'offset': 1},
      \ 'end': {'line': 1, 'offset':1},
      \ 'text': a:message,
      \ 'code': 1005,
      \}]
    endif

    return {
    \ 'seq': 0,
    \ 'type': 'event',
    \ 'event': a:type,
    \ 'body': {'file': expand('%:p'), 'diagnostics': l:diagnostics},
    \}
  endfunction

  function! CreateLoclist(message) abort
    let l:list = []

    if !empty(a:message)
      let l:list = [{
      \ 'lnum': 1,
      \ 'col': 1,
      \ 'end_lnum': 1,
      \ 'end_col': 1,
      \ 'text': a:message,
      \}]
    endif

    return l:list
  endfunction

  call ale#test#SetDirectory('/testplugin/test')
  call ale#test#SetFilename('filename.ts')

  runtime autoload/ale/engine.vim

  let g:ale_buffer_info = {bufnr(''): {'loclist': [], 'active_linter_list': []}}
  let g:ale_handle_loclist_called = 0

  function! ale#engine#HandleLoclist(linter_name, buffer, loclist, from_other_source) abort
    let g:ale_handle_loclist_called = 1
  endfunction

After:
  Restore

  delfunction CreateError
  delfunction CreateLoclist

  call ale#test#RestoreDirectory()

  runtime autoload/ale/engine.vim

Execute(An initial empty list of syntax errors should be ignored):
  call ale#lsp_linter#HandleLSPResponse(1, CreateError('syntaxDiag', ''))

  Assert !g:ale_handle_loclist_called

Execute(An initial list of syntax errors should be handled):
  call ale#lsp_linter#HandleLSPResponse(1, CreateError('syntaxDiag', 'x'))

  Assert g:ale_handle_loclist_called

Execute(Subsequent empty lists should be ignored):
  let g:ale_buffer_info[bufnr('')].syntax_loclist = []

  call ale#lsp_linter#HandleLSPResponse(1, CreateError('syntaxDiag', ''))

  Assert !g:ale_handle_loclist_called

Execute(Empty then non-empty syntax errors should be handled):
  let g:ale_buffer_info[bufnr('')].syntax_loclist = []

  call ale#lsp_linter#HandleLSPResponse(1, CreateError('syntaxDiag', 'x'))

  Assert g:ale_handle_loclist_called

Execute(Non-empty then empty syntax errors should be handled):
  let g:ale_buffer_info[bufnr('')].syntax_loclist = CreateLoclist('x')

  call ale#lsp_linter#HandleLSPResponse(1, CreateError('syntaxDiag', ''))

  Assert g:ale_handle_loclist_called

Execute(Non-empty then non-empty syntax errors should be handled):
  let g:ale_buffer_info[bufnr('')].syntax_loclist = CreateLoclist('x')

  call ale#lsp_linter#HandleLSPResponse(1, CreateError('syntaxDiag', 'x'))

  Assert g:ale_handle_loclist_called

Execute(An initial empty list of semantic errors should be ignored):
  call ale#lsp_linter#HandleLSPResponse(1, CreateError('semanticDiag', ''))

  Assert !g:ale_handle_loclist_called

Execute(An initial list of semantic errors should be handled):
  call ale#lsp_linter#HandleLSPResponse(1, CreateError('semanticDiag', 'x'))

  Assert g:ale_handle_loclist_called

Execute(Subsequent empty lists should be ignored - semantic):
  let g:ale_buffer_info[bufnr('')].semantic_loclist = []

  call ale#lsp_linter#HandleLSPResponse(1, CreateError('semanticDiag', ''))

  Assert !g:ale_handle_loclist_called

Execute(Empty then non-empty semantic errors should be handled):
  let g:ale_buffer_info[bufnr('')].semantic_loclist = []

  call ale#lsp_linter#HandleLSPResponse(1, CreateError('semanticDiag', 'x'))

  Assert g:ale_handle_loclist_called

Execute(Non-empty then empty semantic errors should be handled):
  let g:ale_buffer_info[bufnr('')].semantic_loclist = CreateLoclist('x')

  call ale#lsp_linter#HandleLSPResponse(1, CreateError('semanticDiag', ''))

  Assert g:ale_handle_loclist_called

Execute(Non-empty then non-empty semantic errors should be handled):
  let g:ale_buffer_info[bufnr('')].semantic_loclist = CreateLoclist('x')

  call ale#lsp_linter#HandleLSPResponse(1, CreateError('semanticDiag', 'x'))

  Assert g:ale_handle_loclist_called

Execute(Subsequent empty lists should be ignored - suggestion):
  let g:ale_buffer_info[bufnr('')].suggestion_loclist = []

  call ale#lsp_linter#HandleLSPResponse(1, CreateError('suggestionDiag', ''))

  Assert !g:ale_handle_loclist_called

Execute(Empty then non-empty suggestion messages should be handled):
  let g:ale_buffer_info[bufnr('')].suggestion_loclist = []

  call ale#lsp_linter#HandleLSPResponse(1, CreateError('suggestionDiag', 'x'))

  Assert g:ale_handle_loclist_called

Execute(Non-empty then empt suggestion messages should be handled):
  let g:ale_buffer_info[bufnr('')].suggestion_loclist = CreateLoclist('x')

  call ale#lsp_linter#HandleLSPResponse(1, CreateError('suggestionDiag', ''))

  Assert g:ale_handle_loclist_called

Execute(Non-empty then non-empty suggestion messages should be handled):
  let g:ale_buffer_info[bufnr('')].suggestion_loclist = CreateLoclist('x')

  call ale#lsp_linter#HandleLSPResponse(1, CreateError('suggestionDiag', 'x'))

  Assert g:ale_handle_loclist_called