Add tests for recently added mixins and improve plugin tests

pkg/analyzer_plugin/test/plugin/assist_mixin_test.dart

Index: pkg/analyzer_plugin/test/plugin/assist_mixin_test.dart
diff --git a/pkg/analyzer_plugin/test/plugin/assist_mixin_test.dart b/pkg/analyzer_plugin/test/plugin/assist_mixin_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..9642b160a519d55fed4a1c890d73ccf66e55f5c8
--- /dev/null
+++ b/pkg/analyzer_plugin/test/plugin/assist_mixin_test.dart
@@ -0,0 +1,96 @@
+// 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 'dart:async';
+
+import 'package:analyzer/dart/analysis/results.dart' hide AnalysisResult;
+import 'package:analyzer/file_system/file_system.dart';
+import 'package:analyzer/file_system/memory_file_system.dart';
+import 'package:analyzer/src/dart/analysis/driver.dart';
+import 'package:analyzer_plugin/plugin/assist_mixin.dart';
+import 'package:analyzer_plugin/protocol/protocol_common.dart';
+import 'package:analyzer_plugin/protocol/protocol_generated.dart';
+import 'package:analyzer_plugin/utilities/assist/assist.dart';
+import 'package:path/src/context.dart';
+import 'package:test/test.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
+
+import 'mocks.dart';
+
+void main() {
+  defineReflectiveTests(AssistsMixinTest);
+}
+
+@reflectiveTest
+class AssistsMixinTest {
+  MemoryResourceProvider resourceProvider = new MemoryResourceProvider();
+
+  String packagePath1;
+  String filePath1;
+  ContextRoot contextRoot1;
+
+  MockChannel channel;
+  _TestServerPlugin plugin;
+
+  void setUp() {
+    Context pathContext = resourceProvider.pathContext;
+
+    packagePath1 = resourceProvider.convertPath('/package1');
+    filePath1 = pathContext.join(packagePath1, 'lib', 'test.dart');
+    resourceProvider.newFile(filePath1, '');
+    contextRoot1 = new ContextRoot(packagePath1, <String>[]);
+
+    channel = new MockChannel();
+    plugin = new _TestServerPlugin(resourceProvider);
+    plugin.start(channel);
+  }
+
+  test_handleEditGetAssists() async {
+    await plugin.handleAnalysisSetContextRoots(
+        new AnalysisSetContextRootsParams([contextRoot1]));
+
+    EditGetAssistsResult result = await plugin
+        .handleEditGetAssists(new EditGetAssistsParams(filePath1, 10, 0));
+    expect(result, isNotNull);
+    expect(result.assists, hasLength(3));
+  }
+}
+
+class _TestAssistContributor implements AssistContributor {
+  List<PrioritizedSourceChange> changes;
+
+  _TestAssistContributor(this.changes);
+
+  @override
+  void computeAssists(AssistRequest request, AssistCollector collector) {
+    for (PrioritizedSourceChange change in changes) {
+      collector.addAssist(change);
+    }
+  }
+}
+
+class _TestServerPlugin extends MockServerPlugin with AssistsMixin {
+  _TestServerPlugin(ResourceProvider resourceProvider)
+      : super(resourceProvider);
+
+  PrioritizedSourceChange createChange() {
+    return new PrioritizedSourceChange(0, new SourceChange(''));
+  }
+
+  @override
+  List<AssistContributor> getAssistContributors(AnalysisDriverGeneric driver) {
+    return <AssistContributor>[
+      new _TestAssistContributor(<PrioritizedSourceChange>[createChange()]),
+      new _TestAssistContributor(
+          <PrioritizedSourceChange>[createChange(), createChange()])
+    ];
+  }
+
+  @override
+  Future<ResolveResult> getResolveResultForAssists(
+      AnalysisDriverGeneric driver, String path) async {
+    return new AnalysisResult(
+        null, null, null, null, null, null, null, null, null, null, null);
+  }
+}