Force xunit to display diagnostics for a non-empty collection

Author: tannergooding

tests/ClangSharp.PInvokeGenerator.UnitTests/PInvokeGeneratorTest.cs

@@ -1,8 +1,8 @@
 // Copyright (c) Microsoft and Contributors. All rights reserved. Licensed under the University of Illinois/NCSA Open Source License. See LICENSE.txt in the project root for license information.
-
 using System.Collections.Generic;
 using System.IO;
 using System.Runtime.CompilerServices;
+using System.Text;
 using System.Threading.Tasks;
 using System.Xml.Linq;
 using ClangSharp.Interop;
@@ -75,7 +75,19 @@ private static async Task ValidateGeneratedBindingsAsync(string inputContents, s
 
                 if (expectedDiagnostics is null)
                 {
-                    Assert.Empty(pinvokeGenerator.Diagnostics);
+                    var diagnostics = new StringBuilder();
+
+                    foreach (var diagnostic in pinvokeGenerator.Diagnostics)
+                    {
+                        diagnostics = diagnostics.AppendLine(diagnostic.ToString());
+                    }
+
+                    var diagnosticsString = diagnostics.ToString();
+
+                    if (!string.IsNullOrEmpty(diagnosticsString))
+                    {
+                        throw new System.Exception(diagnosticsString);
+                    }
                 }
                 else
                 {