Add integration tests for the execution domain.

pkg/analysis_server/test/integration/integration_tests.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library test.integration.analysis;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:convert';
 import 'dart:io';
@@ skipping 559 matching lines @@
       if (messageAsMap.containsKey('id')) {
         outOfTestExpect(messageAsMap['id'], isString);
         String id = message['id'];
         Completer completer = _pendingCommands[id];
         if (completer == null) {
           fail('Unexpected response from server: id=$id');
         } else {
           _pendingCommands.remove(id);
         }
         if (messageAsMap.containsKey('error')) {
-          // TODO(paulberry): propagate the error info to the completer.
-          completer.completeError(new UnimplementedError(
-              'Server responded with an error: ${JSON.encode(message)}'));
+          completer.completeError(messageAsMap['error']);

[Paul Berry, 2017/02/12 14:39:04]

I'd recommend making a new class which represents an error received from the
server, and contains the error message JSON as a field (perhaps call the class
"ServerErrorMessage").  That way we can catch the specific exception type
without accidentally catching other exceptions.

[devoncarew, 2017/02/12 17:52:34]

Done.

         } else {
           completer.complete(messageAsMap['result']);
         }
         // Check that the message is well-formed.  We do this after calling
         // completer.complete() or completer.completeError() so that we don't
         // stall the test in the event of an error.
         outOfTestExpect(message, isResponse);
       } else {
         // Message is a notification.  It should have an event and possibly
         // params.
@@ skipping 375 matching lines @@
   void populateMismatches(item, List<MismatchDescriber> mismatches);
 
   /**
    * Create a [MismatchDescriber] describing a mismatch with a simple string.
    */
   MismatchDescriber simpleDescription(String description) =>
       (Description mismatchDescription) {
         mismatchDescription.add(description);
       };
 }