YouCompleteMe/test/diagnostics.test.vim

function! SetUp()
  let g:ycm_use_clangd = 1
  let g:ycm_confirm_extra_conf = 0
  let g:ycm_auto_trigger = 1
  let g:ycm_keep_logfiles = 1
  let g:ycm_log_level = 'DEBUG'
  let g:ycm_always_populate_location_list = 1
  call youcompleteme#test#setup#SetUp()
endfunction

function! TearDown()
  call youcompleteme#test#setup#CleanUp()
endfunction

function! Test_Changing_Filetype_Refreshes_Diagnostics()
  call youcompleteme#test#setup#OpenFile(
        \ '/test/testdata/diagnostics/foo.xml',
        \ { 'native_ft': 0 } )

  call assert_equal( 'xml', &ft )
  call assert_true( pyxeval( 'ycm_state._buffers[' . bufnr( '%' ) . ']._async_diags' ) )
  call assert_equal( [], sign_getplaced() )
  setf typescript
  call assert_equal( 'typescript', &ft )
  call assert_false( pyxeval( 'ycm_state._buffers[' . bufnr( '%' ) . ']._async_diags' ) )
  " Diagnostics are async, so wait for the assert to return 0 for a while.
  call WaitForAssert( {-> assert_equal( 1, len( sign_getplaced() ) ) } )
  call assert_equal( 1, len( sign_getplaced()[ 0 ][ 'signs' ] ) )
  call assert_equal( 'YcmError', sign_getplaced()[ 0 ][ 'signs' ][ 0 ][ 'name' ] )
  call assert_false( empty( getloclist( 0 ) ) )
  %bwipeout!
endfunction

function! Test_MessagePoll_After_LocationList()
  call youcompleteme#test#setup#OpenFile( '/test/testdata/diagnostics/foo.cpp', {} )

  setf cpp
  call assert_equal( 'cpp', &ft )
  call WaitForAssert( {-> assert_equal( 1, len( sign_getplaced() ) ) } )
  call setline( 1, '' )
  doautocmd TextChanged
  call WaitForAssert( {-> assert_true( empty( sign_getplaced() ) ) }, 10000 )
  call assert_true( empty( getloclist( 0 ) ) )
  %bwipeout!
endfunction