Adding a runtimeconfig.dev.json containing the additionalProbePaths when doing dotnet build.

test/dotnet-build.Tests/BuildStandAloneTests.cs

@@ -0,0 +1,50 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System.IO;
+using Microsoft.DotNet.Tools.Test.Utilities;
+using Microsoft.DotNet.ProjectModel;
+using Microsoft.Extensions.PlatformAbstractions;
+using Xunit;
+using System.Linq;
+using Microsoft.DotNet.TestFramework;
+
+namespace Microsoft.DotNet.Tools.Builder.Tests
+{
+    public class BuildStandAloneTests : TestBase
+    {
+        [Fact]
+        public void BuildingAStandAloneProjectProducesARuntimeConfigDevJsonFile()
+        {
+            var testInstance = TestAssetsManager.CreateTestInstance("PortableTests")
+                .WithLockFiles();
+
+            var netstandardappOutput = Build(testInstance);
+
+            netstandardappOutput.Should().Exist().And.HaveFile("StandaloneApp.runtimeconfig.dev.json");
+        }
+
+        public DirectoryInfo Build(TestInstance testInstance)
+        {
+            var projectPath = Path.Combine(testInstance.TestRoot, "StandaloneApp");
+
+            var result = new BuildCommand(
+                projectPath: projectPath)
+                .ExecuteWithCapturedOutput();
+
+            var contexts = ProjectContext.CreateContextForEachFramework(
+                projectPath,
+                null,
+                PlatformServices.Default.Runtime.GetAllCandidateRuntimeIdentifiers());
+
+            var runtime = contexts.FirstOrDefault(c => !string.IsNullOrEmpty(c.RuntimeIdentifier))?.RuntimeIdentifier;
+
+            result.Should().Pass();
+
+            var outputBase = new DirectoryInfo(
+                Path.Combine(testInstance.TestRoot, "StandaloneApp", "bin", "Debug", "netstandardapp1.5"));
+
+            return outputBase.Sub(runtime);
+        }
+    }
+}