dotnet#1074: Add tests

tests/Microsoft.CodeAnalysis.Testing/Microsoft.CodeAnalysis.SourceGenerators.Testing.UnitTests/SourceGeneratorValidationTests.cs

@@ -4,6 +4,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Text;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.CSharp;
@@ -261,6 +262,49 @@ public async Task AddImplicitSimpleFileWithDiagnostic()
             }.RunAsync();
         }
 
+        [Fact]
+        public async Task AddSampleClassWithDefaultCheck()
+        {
+            await new CSharpSourceGeneratorTest<AddSampleClass>
+            {
+                TestState =
+                {
+                    Sources =
+                    {
+                        @"{|#0:|}// Comment",
+                    },
+                    GeneratedSources =
+                    {
+                        ($"Microsoft.CodeAnalysis.Testing.Utilities\\Microsoft.CodeAnalysis.Testing.TestGenerators.{nameof(AddSampleClass)}\\{AddSampleClass.FileName}", SourceText.From(AddSampleClass.GeneratedSource, Encoding.UTF8) )
+                    }
+                },
+            }.RunAsync();
+        }
+
+        [Fact]
+        public async Task AddSampleClassWithCustomCheck()
+        {
+            var test = new CSharpSourceGeneratorTest<AddSampleClass>
+            {
+                TestBehaviors = TestBehaviors.SkipGeneratedSourcesCheck,
+                TestState =
+                {
+                    Sources =
+                    {
+                        @"{|#0:|}// Comment",
+                    },
+                },
+            };
+
+            await test.RunAsync();
+
+            var verifier = new DefaultVerifier();
+            verifier.Equal(1, test.GeneratedTrees.Length);
+            var tree = test.GeneratedTrees[0];
+            verifier.Equal(AddSampleClass.FileName, Path.GetFileName(tree.FilePath));
+            verifier.Equal(AddSampleClass.GeneratedSource, (await tree.GetTextAsync()).ToString());
+        }
+
         private class CSharpSourceGeneratorTest<TSourceGenerator> : SourceGeneratorTest<DefaultVerifier>
             where TSourceGenerator : ISourceGenerator, new()
         {

tests/Microsoft.CodeAnalysis.Testing/Microsoft.CodeAnalysis.Testing.Utilities/TestGenerators/AddSampleClass.cs

@@ -0,0 +1,23 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.CodeAnalysis.Text;
+
+namespace Microsoft.CodeAnalysis.Testing.TestGenerators
+{
+    public class AddSampleClass : ISourceGenerator
+    {
+        public const string FileName = "SampleClass.cs";
+        public const string GeneratedSource = "class Sample {}";
+
+        public void Initialize(GeneratorInitializationContext context)
+        {
+        }
+
+        public virtual void Execute(GeneratorExecutionContext context)
+        {
+            context.AddSource(FileName, GeneratedSource);
+        }
+    }
+}