Before: Save g:ale_buffer_info Save g:ale_enabled let g:ale_buffer_info = {} let g:ale_enabled = 1 let g:expected_loclist = [{ \ 'bufnr': bufnr('%'), \ 'lnum': 2, \ 'vcol': 0, \ 'col': 3, \ 'text': 'foo bar', \ 'type': 'E', \ 'nr': -1, \ 'pattern': '', \ 'valid': 1, \}] function! ToggleTestCallback(buffer, output) return [{ \ 'bufnr': a:buffer, \ 'lnum': 2, \ 'vcol': 0, \ 'col': 3, \ 'text': join(split(a:output[0])), \ 'type': 'E', \ 'nr': -1, \}] endfunction call ale#linter#Define('foobar', { \ 'name': 'testlinter', \ 'callback': 'ToggleTestCallback', \ 'executable': has('win32') ? 'cmd' : 'echo', \ 'command': 'echo foo bar', \}) After: Restore unlet! g:expected_loclist unlet! b:i call ale#engine#Cleanup(bufnr('')) call ale#linter#Reset() let g:ale_buffer_info = {} delfunction ToggleTestCallback Given foobar (Some imaginary filetype): foo bar baz Execute(ALELint should run the linters): AssertEqual 'foobar', &filetype " Try to run the linter a few times, as it fails randomly in NeoVim. for b:i in range(5) ALELint call ale#test#WaitForJobs(2000) if !has('nvim') " Sleep so the delayed list function can run. " This breaks the tests in NeoVim for some reason. sleep 1ms endif if ale#test#GetLoclistWithoutNewerKeys() == g:expected_loclist break endif endfor " Check the loclist AssertEqual g:expected_loclist, ale#test#GetLoclistWithoutNewerKeys()