Before:
  let g:ale_lsp_next_message_id = 1

  function CheckMessage(message, expected_method_name, ...) abort
    if a:0 > 1
        throw 'Too many arguments!'
    endif

    let l:match = matchlist(a:message, '\v^Content-Length: (\d+)' . "\r\n\r\n" . '(.+)$')

    if empty(l:match)
      Assert 0, 'Invalid message format: ' . a:message
    endif

    if strlen(l:match[2]) < str2nr(l:match[1])
      Assert 0, 'Invalid Content-Length (' . l:match[1] . ') :' . a:message
    endif

    let l:expected_json = {
    \   'id': g:ale_lsp_next_message_id - 1,
    \   'jsonrpc': '2.0',
    \   'method': a:expected_method_name,
    \}

    if a:0 > 0
      let l:expected_json.params = a:1
    endif

    AssertEqual l:expected_json, json_decode(l:match[2])
  endfunction

  function Range(start_line, start_char, end_line, end_char) abort
    return {
    \ 'start': {'line': a:start_line, 'character': a:start_char},
    \ 'end': {'line': a:end_line, 'character': a:end_char},
    \}
  endfunction

After:
  delfunction CheckMessage
  delfunction Range

Execute(GetNextMessageID() should increment appropriately):
  " We should get the initial ID, and increment a bit.
  AssertEqual 1, ale#lsp#GetNextMessageID()
  AssertEqual 2, ale#lsp#GetNextMessageID()
  AssertEqual 3, ale#lsp#GetNextMessageID()

  " Set the maximum ID.
  let g:ale_lsp_next_message_id = 9223372036854775807

  " When we hit the maximum ID, the next ID afterwards should be 1.
  AssertEqual 9223372036854775807, ale#lsp#GetNextMessageID()
  AssertEqual 1, ale#lsp#GetNextMessageID()

Execute(ale#lsp#CreateMessage() should create an appropriate message):
    " 71 is the size in bytes for UTF-8, not the number of characters.
    AssertEqual
    \   "Content-Length: 71\r\n\r\n"
    \   . '{"id":1,"jsonrpc":"2.0","method":"someMethod","params":{"foo":"barÜ"}}',
    \ ale#lsp#CreateMessage('someMethod', {'foo': 'barÜ'})
    " Check again to ensure that we use the next ID.
    AssertEqual
    \   "Content-Length: 71\r\n\r\n"
    \   . '{"id":2,"jsonrpc":"2.0","method":"someMethod","params":{"foo":"barÜ"}}',
    \ ale#lsp#CreateMessage('someMethod', {'foo': 'barÜ'})

Execute(ale#lsp#ReadMessage() should read messages correctly):
  AssertEqual
  \  {'id': 2, 'jsonrpc': '2.0', 'result': {'foo': 'barÜ'}},
  \ ale#lsp#ReadMessage(
  \   "Content-Length: 49\r\n\r\n"
  \   . '{"id":2,"jsonrpc":"2.0","result":{"foo":"barÜ"}}'
  \ )

Execute(ale#lsp#message#Initialize() should return correct messages):
  call CheckMessage(
  \ ale#lsp#message#Initialize(123, '/foo/bar'),
  \ 'initialize',
  \ {
  \   'processId': 123,
  \   'rootUri': '/foo/bar',
  \   'capabilities': {},
  \ }
  \)

Execute(ale#lsp#message#Initialized() should return correct messages):
  call CheckMessage(ale#lsp#message#Initialized(), 'initialized')

Execute(ale#lsp#message#Shutdown() should return correct messages):
  call CheckMessage(ale#lsp#message#Shutdown(), 'shutdown')

Execute(ale#lsp#message#Exit() should return correct messages):
  call CheckMessage(ale#lsp#message#Exit(), 'exit')

Execute(ale#lsp#message#DidOpen() should return correct messages):
  call CheckMessage(
  \ ale#lsp#message#DidOpen('/foo/bar', 'typescript', 123, 'foobar'),
  \ 'textDocument/didOpen',
  \ {
  \   'textDocument': {
  \       'uri': '/foo/bar',
  \       'languageId': 'typescript',
  \       'version': 123,
  \       'text': 'foobar',
  \   },
  \ }
  \)

Execute(ale#lsp#message#DidChange() should return correct messages):
  call CheckMessage(
  \ ale#lsp#message#DidChange('/foo/bar', 123, 'foobar'),
  \ 'textDocument/didChange',
  \ {
  \   'textDocument': {
  \       'uri': '/foo/bar',
  \       'version': 123,
  \   },
  \   'contentChanges': [{'text': 'foobar'}]
  \ }
  \)

Execute(ale#lsp#message#DidSave() should return correct messages):
  call CheckMessage(
  \ ale#lsp#message#DidSave('/foo/bar'),
  \ 'textDocument/didSave',
  \ {
  \   'textDocument': {
  \       'uri': '/foo/bar',
  \   },
  \ }
  \)

Execute(ale#lsp#message#DidClose() should return correct messages):
  call CheckMessage(
  \ ale#lsp#message#DidClose('/foo/bar'),
  \ 'textDocument/didClose',
  \ {
  \   'textDocument': {
  \       'uri': '/foo/bar',
  \   },
  \ }
  \)

Execute(ale#lsp#ReadDiagnostics() should handle errors):
  AssertEqual ['filename.ts', [
  \   {
  \     'type': 'E',
  \     'message': 'Something went wrong!',
  \     'lnum': 3,
  \     'col': 11,
  \     'end_lnum': 5,
  \     'end_col': 16,
  \     'nr': 'some-error',
  \   }
  \ ]],
  \ ale#lsp#ReadDiagnostics({'uri': 'filename.ts', 'diagnostics': [
  \   {
  \     'severity': 1,
  \     'range': Range(2, 10, 4, 15),
  \     'code': 'some-error',
  \     'message': 'Something went wrong!',
  \   },
  \ ]})

Execute(ale#lsp#ReadDiagnostics() should handle warnings):
  AssertEqual ['filename.ts', [
  \   {
  \     'type': 'W',
  \     'message': 'Something went wrong!',
  \     'lnum': 2,
  \     'col': 4,
  \     'end_lnum': 2,
  \     'end_col': 4,
  \     'nr': 'some-warning',
  \   }
  \ ]],
  \ ale#lsp#ReadDiagnostics({'uri': 'filename.ts', 'diagnostics': [
  \   {
  \     'severity': 2,
  \     'range': Range(1, 3, 1, 3),
  \     'code': 'some-warning',
  \     'message': 'Something went wrong!',
  \   },
  \ ]})

Execute(ale#lsp#ReadDiagnostics() should treat messages with missing severity as errors):
  AssertEqual ['filename.ts', [
  \   {
  \     'type': 'E',
  \     'message': 'Something went wrong!',
  \     'lnum': 3,
  \     'col': 11,
  \     'end_lnum': 5,
  \     'end_col': 16,
  \     'nr': 'some-error',
  \   }
  \ ]],
  \ ale#lsp#ReadDiagnostics({'uri': 'filename.ts', 'diagnostics': [
  \   {
  \     'range': Range(2, 10, 4, 15),
  \     'code': 'some-error',
  \     'message': 'Something went wrong!',
  \   },
  \ ]})

Execute(ale#lsp#ReadDiagnostics() should handle messages without codes):
  AssertEqual ['filename.ts', [
  \   {
  \     'type': 'E',
  \     'message': 'Something went wrong!',
  \     'lnum': 3,
  \     'col': 11,
  \     'end_lnum': 5,
  \     'end_col': 16,
  \   }
  \ ]],
  \ ale#lsp#ReadDiagnostics({'uri': 'filename.ts', 'diagnostics': [
  \   {
  \     'range': Range(2, 10, 4, 15),
  \     'message': 'Something went wrong!',
  \   },
  \ ]})

Execute(ale#lsp#ReadDiagnostics() should handle multiple messages):
  AssertEqual ['filename.ts', [
  \   {
  \     'type': 'E',
  \     'message': 'Something went wrong!',
  \     'lnum': 1,
  \     'col': 3,
  \     'end_lnum': 1,
  \     'end_col': 3,
  \   },
  \   {
  \     'type': 'W',
  \     'message': 'A warning',
  \     'lnum': 2,
  \     'col': 5,
  \     'end_lnum': 2,
  \     'end_col': 5,
  \   },
  \ ]],
  \ ale#lsp#ReadDiagnostics({'uri': 'filename.ts', 'diagnostics': [
  \   {
  \     'range': Range(0, 2, 0, 2),
  \     'message': 'Something went wrong!',
  \   },
  \   {
  \     'severity': 2,
  \     'range': Range(1, 4, 1, 4),
  \     'message': 'A warning',
  \   },
  \ ]})