Before:
  let g:expected_loclist = [{
  \ 'bufnr': bufnr('%'),
  \ 'lnum': 2,
  \ 'vcol': 0,
  \ 'col': 3,
  \ 'text': 'foo bar',
  \ 'type': 'E',
  \ 'nr': -1,
  \ 'pattern': '',
  \ 'valid': 1,
  \}]
  let g:expected_groups = [
  \ 'ALECleanupGroup',
  \ 'ALECursorGroup',
  \ 'ALEHighlightBufferGroup',
  \ 'ALERunOnEnterGroup',
  \ 'ALERunOnTextChangedGroup',
  \]

  function! ToggleTestCallback(buffer, output)
    return [{
    \ 'bufnr': a:buffer,
    \ 'lnum': 2,
    \ 'vcol': 0,
    \ 'col': 3,
    \ 'text': a:output[0],
    \ 'type': 'E',
    \ 'nr': -1,
    \}]
  endfunction

  call ale#linter#Define('foobar', {
  \ 'name': 'testlinter',
  \ 'callback': 'ToggleTestCallback',
  \ 'executable': 'echo',
  \ 'command': 'echo foo bar',
  \})

After:
  unlet! g:expected_loclist
  unlet! g:expected_groups

  let g:ale_buffer_info = {}
  call ale#linter#Reset()

  delfunction ToggleTestCallback

Given foobar (Some imaginary filetype):
  foo
  bar
  baz

Execute(ALELint should run the linters):
  AssertEqual 'foobar', &filetype

  ALELint
  call ale#engine#WaitForJobs(2000)

  " Check the loclist
  AssertEqual g:expected_loclist, getloclist(0)