Add an integration test to verify that server I/O is asynchronous.

pkg/analysis_server/test/integration/asynchrony_test.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.error;
+
+import 'dart:async';
+
+import 'package:unittest/unittest.dart';
+
+import '../reflective_tests.dart';
+import 'integration_tests.dart';
+
+/**
+ * Verify that the server's input and output streams are asynchronous by
+ * attempting to flood its input buffer with commands without listening to
+ * its output buffer for responses.  The server should continue to train its
+ * input buffer even though its output buffer is full.
+ *
+ * Once enough commands have been sent, we begin reading from the server's
+ * output buffer, and verify that it responds to the last command.
+ */
+@ReflectiveTestCase()
+class AsynchronyIntegrationTest {
+  /**
+   * Connection to the analysis server.
+   */
+  final Server server = new Server();
+
+  /**
+   * Number of messages to queue up before listening for responses.
+   */
+  static const MESSAGE_COUNT = 10000;
+
+  Future setUp() {
+    return server.start();
+  }
+
+  test_asynchrony() {
+    // Send MESSAGE_COUNT messages to the server without listening for
+    // responses.
+    Future lastMessageResult;
+    for (int i = 0; i < MESSAGE_COUNT; i++) {
+      lastMessageResult = server.send('server.getVersion', null);
+    }
+
+    // Flush the server's standard input stream to verify that it has really
+    // received them all.  If the server is blocked waiting for us to read
+    // its responses, the flush will never complete.
+    return server.flushCommands().then((_) {

[danrubel, 2014/10/22 14:56:14]

Is it possible to add a timeout for the flushCommands so that the test will
continue and fail rather than blocking forever? Does that make sense?

+
+      // Begin processing responses from the server.
+      server.listenToOutput((String event, params) {
+        // No notifications are expected.
+        fail('Unexpected notification: $event');
+      });
+
+      // Terminate the test when the response to the last message is received.
+      lastMessageResult.then((_) {
+        server.send("server.shutdown", null).then((_) {
+          return server.exitCode;
+        });
+      });
+    });
+  }
+}
+
+main() {
+  runReflectiveTests(AsynchronyIntegrationTest);
+}