Add a test for design time builds #1846

This change adds a test to verify that Razor targets don't show up in
design time builds when RazorCompileOnBuild=true

We don't want to add a significant perf cost to design time builds since
they affect project load.

test/Microsoft.AspNetCore.Razor.Design.Test/IntegrationTests/DesignTimeBuildIntegrationTest.cs

@@ -0,0 +1,34 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Threading.Tasks;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Razor.Design.IntegrationTests
+{
+    public class DesignTimeBuildIntegrationTest : MSBuildIntegrationTestBase
+    {
+        [Fact]
+        [InitializeTestProject("SimpleMvc")]
+        public async Task DesignTimeBuild_DoesNotRunRazorTargets()
+        {
+            // Using Compile here instead of CompileDesignTime because the latter is only defined when using
+            // the VS targets. This is a close enough simulation for an SDK project
+            var result = await DotnetMSBuild("Compile", "/p:RazorCompileOnBuild=true /p:DesignTimeBuild=true /clp:PerformanceSummary");
+
+            Assert.BuildPassed(result);
+            Assert.FileDoesNotExist(result, OutputPath, "SimpleMvc.dll");
+            Assert.FileDoesNotExist(result, OutputPath, "SimpleMvc.pdb");
+            Assert.FileDoesNotExist(result, OutputPath, "SimpleMvc.PrecompiledViews.dll");
+            Assert.FileDoesNotExist(result, OutputPath, "SimpleMvc.PrecompiledViews.pdb");
+            
+            // This target should be part of the design time build.
+            Assert.Contains("RazorGetAssemblyAttributes", result.Output);
+
+            // We don't want to see the expensive Razor targets in the performance summary, since they shouldn't run
+            // during a design time build.
+            Assert.DoesNotContain("RazorCoreGenerate", result.Output);
+            Assert.DoesNotContain("RazorCoreCompile", result.Output);
+        }
+    }
+}