Make sure that netcoreapp2.1 test execution is testing the netcoreapp2.1 build of ImageSharp

src/ImageSharp/Common/Helpers/TestHelpers.cs

@@ -0,0 +1,24 @@
+// Copyright(c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+namespace SixLabors.ImageSharp.Common.Helpers
+{
+    /// <summary>
+    /// Internal utilities intended to be only used in tests.
+    /// </summary>
+    internal static class TestHelpers
+    {
+        /// <summary>
+        /// This constant is useful to verify the target framework ImageSharp has been built against.
+        /// Only intended to be used in tests!
+        /// </summary>
+        internal const string ImageSharpBuiltAgainst =
+#if NETSTANDARD1_1
+            "netstandard1.1";
+#elif NETCOREAPP2_1
+            "netcoreapp2.1";
+#else
+            "netstandard2.0";
+#endif
+    }
+}

tests/ImageSharp.Tests/TestUtilities/TestEnvironment.cs

@@ -30,6 +30,13 @@ namespace SixLabors.ImageSharp.Tests
                     return Boolean.TryParse(Environment.GetEnvironmentVariable("CI"), out isCi) && isCi;
                 });
 
+        private static readonly Lazy<string> NetCoreVersionLazy = new Lazy<string>(GetNetCoreVersion);
+
+        /// <summary>
+        /// Gets the .NET Core version, if running on .NET Core, otherwise returns null.
+        /// </summary>
+        internal static string NetCoreVersion => NetCoreVersionLazy.Value;
+
         // ReSharper disable once InconsistentNaming
         /// <summary>
         /// Gets a value indicating whether test execution runs on CI.
@@ -123,5 +130,19 @@ namespace SixLabors.ImageSharp.Tests
 
             return path;
         }
+
+        /// <summary>
+        /// Solution borrowed from:
+        /// https://github.com/dotnet/BenchmarkDotNet/issues/448#issuecomment-308424100
+        /// </summary>
+        private static string GetNetCoreVersion()
+        {
+            Assembly assembly = typeof(System.Runtime.GCSettings).GetTypeInfo().Assembly;
+            string[] assemblyPath = assembly.CodeBase.Split(new[] { '/', '\\' }, StringSplitOptions.RemoveEmptyEntries);
+            int netCoreAppIndex = Array.IndexOf(assemblyPath, "Microsoft.NETCore.App");
+            if (netCoreAppIndex > 0 && netCoreAppIndex < assemblyPath.Length - 2)
+                return assemblyPath[netCoreAppIndex + 1];
+            return "";
+        }
     }
 }

tests/ImageSharp.Tests/TestUtilities/Tests/TestEnvironmentTests.cs

@@ -4,6 +4,7 @@
 using System;
 using System.IO;
 
+using SixLabors.ImageSharp.Common.Helpers;
 using SixLabors.ImageSharp.Formats;
 using SixLabors.ImageSharp.Formats.Bmp;
 using SixLabors.ImageSharp.Formats.Gif;
@@ -13,9 +14,11 @@ using SixLabors.ImageSharp.Tests.TestUtilities.ReferenceCodecs;
 
 using Xunit;
 using Xunit.Abstractions;
+// ReSharper disable InconsistentNaming
 
 namespace SixLabors.ImageSharp.Tests
 {
+    
     public class TestEnvironmentTests
     {
         public TestEnvironmentTests(ITestOutputHelper output)
@@ -31,6 +34,29 @@ namespace SixLabors.ImageSharp.Tests
             Assert.True(Directory.Exists(path));
         }
 
+        /// <summary>
+        /// We need this test to make sure that the netcoreapp2.1 test execution actually covers the netcoreapp2.1 build configuration of ImageSharp.
+        /// </summary>
+        [Fact]
+        public void ImageSharpAssemblyUnderTest_MatchesExpectedTargetFramework()
+        {
+            this.Output.WriteLine("NetCoreVersion: " + TestEnvironment.NetCoreVersion);
+            this.Output.WriteLine("ImageSharpBuiltAgainst: " + TestHelpers.ImageSharpBuiltAgainst);
+
+            if (string.IsNullOrEmpty(TestEnvironment.NetCoreVersion))
+            {
+                this.Output.WriteLine("Not running under .NET Core!");
+            }
+            else if (TestEnvironment.NetCoreVersion.StartsWith("2.1"))
+            {
+                Assert.Equal("netcoreapp2.1", TestHelpers.ImageSharpBuiltAgainst);
+            }
+            else
+            {
+                Assert.Equal("netstandard2.0", TestHelpers.ImageSharpBuiltAgainst);
+            }
+        }
+
         [Fact]
         public void SolutionDirectoryFullPath()
         {