Add an integration test for diagnostics.getDiagnostics.

pkg/analysis_server/test/integration/diagnostic/get_diagnostics_test.dart

+// Copyright (c) 2017, 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.
+
+import 'package:analysis_server/plugin/protocol/protocol.dart';
+import 'package:test/test.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
+
+import '../integration_tests.dart';
+
+main() {
+  defineReflectiveSuite(() {
+    defineReflectiveTests(GetDiagnosticsTest);
+  });
+}
+
+@reflectiveTest
+class GetDiagnosticsTest extends AbstractAnalysisServerIntegrationTest {
+  test_getDiagnostics() async {
+    standardAnalysisSetup();
+
+    DiagnosticGetDiagnosticsResult result =
+        await sendDiagnosticGetDiagnostics();
+
+    // Do some lightweight validation of the returned data.
+    expect(result.contexts, hasLength(1));
+    ContextData context = result.contexts.first;
+    expect(context.name, isNotEmpty);
+  }
+
+  @override
+  bool get enableNewAnalysisDriver => true;
+}