Add C# tests.

src/EditorFeatures/CSharpTest/CSharpEditorServicesTest.csproj

@@ -93,8 +93,10 @@
     <AssemblyName>Roslyn.Services.Editor.CSharp.UnitTests</AssemblyName>
     <RoslynProjectType>UnitTest</RoslynProjectType>
   </PropertyGroup>
-  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' "></PropertyGroup>
-  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' "></PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
+  </PropertyGroup>
   <ItemGroup>
     <Reference Include="Microsoft.CSharp" />
     <Reference Include="PresentationCore" />
@@ -278,6 +280,7 @@
     <Compile Include="Formatting\Indentation\SmartTokenFormatterFormatTokenTests.cs" />
     <Compile Include="InlineDeclaration\CSharpInlineDeclarationTests_FixAllTests.cs" />
     <Compile Include="InlineDeclaration\CSharpInlineDeclarationTests.cs" />
+    <Compile Include="UseCollectionInitializer\UseCollectionInitializerTests.cs" />
     <Compile Include="UsePatternMatching\CSharpIsAndCastCheckTests_FixAllTests.cs" />
     <Compile Include="UsePatternMatching\CSharpIsAndCastCheckTests.cs" />
     <Compile Include="UsePatternMatching\CSharpAsAndNullCheckTests.cs" />

src/EditorFeatures/CSharpTest/UseCollectionInitializer/UseCollectionInitializerTests.cs

+// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
+
+using System;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.CodeFixes;
+using Microsoft.CodeAnalysis.CSharp.UseCollectionInitializer;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Microsoft.CodeAnalysis.Editor.CSharp.UnitTests.Diagnostics;
+using Roslyn.Test.Utilities;
+using Xunit;
+
+namespace Microsoft.CodeAnalysis.Editor.CSharp.UnitTests.UseCollectionInitializer
+{
+    public partial class UseCollectionInitializerTests : AbstractCSharpDiagnosticProviderBasedUserDiagnosticTest
+    {
+        internal override Tuple<DiagnosticAnalyzer, CodeFixProvider> CreateDiagnosticProviderAndFixer(Workspace workspace)
+        {
+            return new Tuple<DiagnosticAnalyzer, CodeFixProvider>(
+                new CSharpUseCollectionInitializerDiagnosticAnalyzer(),
+                new CSharpUseCollectionInitializerCodeFixProvider());
+        }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsUseCollectionInitializer)]
+        public async Task TestOnVariableDeclarator()
+        {
+            await TestAsync(
+@"
+using System.Collections.Generic;
+class C
+{
+    void M()
+    {
+        var c = [||]new List<int>();
+        c.Add(1);
+    }
+}",
+@"
+using System.Collections.Generic;
+class C
+{
+    void M()
+    {
+        var c = new List<int>()
+        {
+            1
+        };
+    }
+}");
+        }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsUseCollectionInitializer)]
+        public async Task TestOnAssignmentExpression()
+        {
+            await TestAsync(
+@"
+using System.Collections.Generic;
+class C
+{
+    void M()
+    {
+        List<int> c = null;
+        c = [||]new List<int>();
+        c.Add(1);
+    }
+}",
+@"
+using System.Collections.Generic;
+class C
+{
+    void M()
+    {
+        List<int> c = null;
+        c = new List<int>()
+        {
+            1
+        };
+    }
+}");
+        }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsUseCollectionInitializer)]
+        public async Task TestMissingOnRefAdd()
+        {
+            await TestMissingAsync(
+@"
+using System.Collections.Generic;
+class C
+{
+    void M()
+    {
+        var c = [||]new List<int>();
+        c.Add(ref i);
+    }
+}");
+        }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsUseCollectionInitializer)]
+        public async Task TestComplexInitializer()
+        {
+            await TestAsync(
+@"
+using System.Collections.Generic;
+class C
+{
+    void M()
+    {
+        List<int>[] array;
+
+        array[0] = [||]new List<int>();
+        array[0].Add(1);
+        array[0].Add(2);
+    }
+}",
+@"
+using System.Collections.Generic;
+class C
+{
+    void M()
+    {
+        List<int>[] array;
+
+        array[0] = new List<int>()
+        {
+            1,
+            2
+        };
+    }
+}");
+        }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsUseCollectionInitializer)]
+        public async Task TestNotOnNamedArg()
+        {
+            await TestMissingAsync(
+@"
+using System.Collections.Generic;
+class C
+{
+    void M()
+    {
+        var c = [||]new List<int>();
+        c.Add(arg: 1);
+    }
+}");
+        }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsUseCollectionInitializer)]
+        public async Task TestMissingWithExistingInitializer()
+        {
+            await TestMissingAsync(
+@"
+using System.Collections.Generic;
+class C
+{
+    void M()
+    {
+        var c = [||]new List<int>() { 1 };
+        c.Add(1);
+    }
+}");
+        }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsUseCollectionInitializer)]
+        public async Task TestFixAllInDocument()
+        {
+            await TestAsync(
+@"
+using System.Collections.Generic;
+class C
+{
+    void M()
+    {
+        List<int>[] array;
+
+        array[0] = {|FixAllInDocument:new|} List<int>();
+        array[0].Add(1);
+        array[0].Add(2);
+
+        array[1] = new List<int>();
+        array[1].Add(3);
+        array[1].Add(4);
+    }
+}",
+@"
+using System.Collections.Generic;
+class C
+{
+    void M()
+    {
+        List<int>[] array;
+
+        array[0] = new List<int>()
+        {
+            1,
+            2
+        };
+        array[1] = new List<int>()
+        {
+            3,
+            4
+        };
+    }
+}");
+        }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsUseCollectionInitializer)]
+        public async Task TestTrivia1()
+        {
+            await TestAsync(
+@"
+using System.Collections.Generic;
+class C
+{
+    void M()
+    {
+        var c = [||]new List<int>();
+        c.Add(1); // Foo
+        c.Add(2); // Bar
+    }
+}",
+@"
+using System.Collections.Generic;
+class C
+{
+    void M()
+    {
+        var c = new List<int>()
+        {
+            1, // Foo
+            2 // Bar
+        };
+    }
+}",
+compareTokens: false);
+        }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsUseCollectionInitializer)]
+        public async Task TestComplexInitializer2()
+        {
+            await TestAsync(
+@"
+using System.Collections.Generic;
+class C
+{
+    void M()
+    {
+        var c = new [||]Dictionary<int, string>();
+        c.Add(1, ""x"");
+        c.Add(2, ""y"");
+    }
+}",
+@"
+using System.Collections.Generic;
+class C
+{
+    void M()
+    {
+        var c = new Dictionary<int, string>()
+        {
+            { 1, ""x"" },
+            { 2, ""y"" }
+        };
+    }
+}");
+        }
+    }
+}
\ No newline at end of file

src/EditorFeatures/TestUtilities/Traits.cs

@@ -84,6 +84,7 @@ public static class Features
             public const string CodeActionsSpellcheck = "CodeActions.Spellcheck";
             public const string CodeActionsSuppression = "CodeActions.Suppression";
             public const string CodeActionsUseAutoProperty = "CodeActions.UseAutoProperty";
+            public const string CodeActionsUseCollectionInitializer = "CodeActions.UseCollectionInitializer";
             public const string CodeActionsUseExpressionBody = "CodeActions.UseExpressionBody";
             public const string CodeActionsUseImplicitType = "CodeActions.UseImplicitType";
             public const string CodeActionsUseExplicitType = "CodeActions.UseExplicitType";