Before:
  Save g:ale_buffer_info

  let g:ale_buffer_info = {}

  " A function for conveniently creating expected count objects.
  function! Counts(data) abort
    let l:res = {
    \   '0': 0,
    \   '1': 0,
    \   'error': 0,
    \   'warning': 0,
    \   'info': 0,
    \   'style_error': 0,
    \   'style_warning': 0,
    \   'total': 0,
    \}

    for l:key in keys(a:data)
      let l:res[l:key] = a:data[l:key]
    endfor

    let l:res[0] = l:res.error + l:res.style_error
    let l:res[1] = l:res.warning + l:res.style_warning + l:res.info
    let l:res.total = l:res[0] + l:res[1]

    return l:res
  endfunction

  " A test simplified loclist that will be used for some of the
  " tests in this module.
  let g:test_buffer_info = {
  \ bufnr(''): {
  \   'loclist': [
  \     {'bufnr': bufnr('') - 1, 'type': 'E'},
  \     {'bufnr': bufnr('') - 1, 'type': 'E', 'sub_type': 'style'},
  \     {'bufnr': bufnr('') - 1, 'type': 'W'},
  \     {'bufnr': bufnr('') - 1, 'type': 'W', 'sub_type': 'style'},
  \     {'bufnr': bufnr('') - 1, 'type': 'I'},
  \     {'bufnr': bufnr(''), 'type': 'E'},
  \     {'bufnr': bufnr(''), 'type': 'E', 'sub_type': 'style'},
  \     {'bufnr': bufnr(''), 'type': 'E', 'sub_type': 'style'},
  \     {'bufnr': bufnr(''), 'type': 'W'},
  \     {'bufnr': bufnr(''), 'type': 'W'},
  \     {'bufnr': bufnr(''), 'type': 'W'},
  \     {'bufnr': bufnr(''), 'type': 'W', 'sub_type': 'style'},
  \     {'bufnr': bufnr(''), 'type': 'W', 'sub_type': 'style'},
  \     {'bufnr': bufnr(''), 'type': 'W', 'sub_type': 'style'},
  \     {'bufnr': bufnr(''), 'type': 'W', 'sub_type': 'style'},
  \     {'bufnr': bufnr(''), 'type': 'I'},
  \     {'bufnr': bufnr(''), 'type': 'I'},
  \     {'bufnr': bufnr(''), 'type': 'I'},
  \     {'bufnr': bufnr(''), 'type': 'I'},
  \     {'bufnr': bufnr(''), 'type': 'I'},
  \     {'bufnr': bufnr('') + 1, 'type': 'E'},
  \     {'bufnr': bufnr('') + 1, 'type': 'E', 'sub_type': 'style'},
  \     {'bufnr': bufnr('') + 1, 'type': 'W'},
  \     {'bufnr': bufnr('') + 1, 'type': 'W', 'sub_type': 'style'},
  \     {'bufnr': bufnr('') + 1, 'type': 'I'},
  \   ],
  \ },
  \}
After:
  Restore

  delfunction Counts
  unlet g:test_buffer_info

Execute (Count should be 0 when data is empty):
  AssertEqual Counts({}), ale#statusline#Count(bufnr(''))

Execute (FirstProblem should be 0 when data is empty):
  AssertEqual {}, ale#statusline#FirstProblem(bufnr(''), 'error')
  AssertEqual {}, ale#statusline#FirstProblem(bufnr(''), 'warning')
  AssertEqual {}, ale#statusline#FirstProblem(bufnr(''), 'style_error')
  AssertEqual {}, ale#statusline#FirstProblem(bufnr(''), 'style_warning')
  AssertEqual {}, ale#statusline#FirstProblem(bufnr(''), 'info')

Execute (Count should read data from the cache):
  let g:ale_buffer_info = {'44': {'count': Counts({'error': 1, 'warning': 2})}}
  AssertEqual Counts({'error': 1, 'warning': 2}), ale#statusline#Count(44)

Execute (FirstProblem should read data from the cache):
  let g:ale_buffer_info =
    \{"44":
        \{'count': 0,
         \'first_problems':
              \{'error': {'lnum': 3},
              \'warning': {'lnum': 44},
              \'style_error': {'lnum': 22},
              \'style_warning': {'lnum': 223},
              \'info': {'lnum': 2}
           \}
        \}
    \}
  AssertEqual {'lnum': 3}, ale#statusline#FirstProblem(44, 'error')
  AssertEqual {'lnum': 44}, ale#statusline#FirstProblem(44, 'warning')
  AssertEqual {'lnum': 223}, ale#statusline#FirstProblem(44, 'style_warning')
  AssertEqual {'lnum': 22}, ale#statusline#FirstProblem(44, 'style_error')
  AssertEqual {'lnum': 2}, ale#statusline#FirstProblem(44, 'info')

Execute (The count should be correct after an update):
  let g:ale_buffer_info = {'44': {}}
  call ale#statusline#Update(44, [])
  AssertEqual Counts({}), ale#statusline#Count(44)

Execute (FirstProblem should be correct after an update):
  let g:ale_buffer_info = {'44': {}}
  call ale#statusline#Update(44, [])
  AssertEqual {}, ale#statusline#FirstProblem(bufnr(''), 'error')
  AssertEqual {}, ale#statusline#FirstProblem(bufnr(''), 'warning')
  AssertEqual {}, ale#statusline#FirstProblem(bufnr(''), 'style_error')
  AssertEqual {}, ale#statusline#FirstProblem(bufnr(''), 'style_warning')
  AssertEqual {}, ale#statusline#FirstProblem(bufnr(''), 'info')

Execute (Count should match the loclist):
  let g:ale_buffer_info = g:test_buffer_info
  AssertEqual {
  \ 'error': 1,
  \ 'style_error': 2,
  \ 'warning': 3,
  \ 'style_warning': 4,
  \ 'info': 5,
  \ '0': 3,
  \ '1': 12,
  \ 'total': 15,
  \}, ale#statusline#Count(bufnr(''))

Execute (FirstProblem should pull the first matching value from the loclist):
  let g:ale_buffer_info = g:test_buffer_info
  AssertEqual {'bufnr': bufnr(''), 'type': 'E'}, ale#statusline#FirstProblem(bufnr(''), 'error')
  AssertEqual {'bufnr': bufnr(''), 'type': 'W'}, ale#statusline#FirstProblem(bufnr(''), 'warning')
  AssertEqual {'bufnr': bufnr(''), 'type': 'E', 'sub_type': 'style'}, ale#statusline#FirstProblem(bufnr(''), 'style_error')
  AssertEqual {'bufnr': bufnr(''), 'type': 'W', 'sub_type': 'style'}, ale#statusline#FirstProblem(bufnr(''), 'style_warning')
  AssertEqual {'bufnr': bufnr(''), 'type': 'I'}, ale#statusline#FirstProblem(bufnr(''), 'info')

Execute (Output should be empty for non-existent buffer):
  let g:ale_buffer_info = g:test_buffer_info
  AssertEqual Counts({}), ale#statusline#Count(9001)
  AssertEqual {}, ale#statusline#FirstProblem(9001, 'error')
  AssertEqual {}, ale#statusline#FirstProblem(9001, 'warning')
  AssertEqual {}, ale#statusline#FirstProblem(9001, 'style_error')
  AssertEqual {}, ale#statusline#FirstProblem(9001, 'style_warning')
  AssertEqual {}, ale#statusline#FirstProblem(9001, 'info')
