Add HeaderEnumerator tests (#19585)

src/Servers/Kestrel/Core/test/Http2HeadersEnumeratorTests.cs

@@ -0,0 +1,88 @@
+// 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.Collections.Generic;
+using System.Linq;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http;
+using Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http2;
+using Microsoft.Extensions.Primitives;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
+{
+    public class Http2HeadersEnumeratorTests
+    {
+        [Fact]
+        public void CanIterateOverResponseHeaders()
+        {
+            var responseHeaders = new HttpResponseHeaders
+            {
+                ContentLength = 9,
+                HeaderAcceptRanges = "AcceptRanges!",
+                HeaderAge = new StringValues(new[] { "1", "2" }),
+                HeaderDate = "Date!"
+            };
+            responseHeaders.Append("Name1", "Value1");
+            responseHeaders.Append("Name2", "Value2-1");
+            responseHeaders.Append("Name2", "Value2-2");
+            responseHeaders.Append("Name3", "Value3");
+
+            var e = new Http2HeadersEnumerator();
+            e.Initialize(responseHeaders);
+
+            var headers = GetNormalizedHeaders(e);
+
+            Assert.Equal(new[]
+            {
+                new KeyValuePair<string, string>("Date", "Date!"),
+                new KeyValuePair<string, string>("Accept-Ranges", "AcceptRanges!"),
+                new KeyValuePair<string, string>("Age", "1"),
+                new KeyValuePair<string, string>("Age", "2"),
+                new KeyValuePair<string, string>("Content-Length", "9"),
+                new KeyValuePair<string, string>("Name1", "Value1"),
+                new KeyValuePair<string, string>("Name2", "Value2-1"),
+                new KeyValuePair<string, string>("Name2", "Value2-2"),
+                new KeyValuePair<string, string>("Name3", "Value3"),
+            }, headers);
+        }
+
+        [Fact]
+        public void CanIterateOverResponseTrailers()
+        {
+            var responseHeaders = new HttpResponseTrailers
+            {
+                ContentLength = 9,
+                HeaderETag = "ETag!"
+            };
+            responseHeaders.Append("Name1", "Value1");
+            responseHeaders.Append("Name2", "Value2-1");
+            responseHeaders.Append("Name2", "Value2-2");
+            responseHeaders.Append("Name3", "Value3");
+
+            var e = new Http2HeadersEnumerator();
+            e.Initialize(responseHeaders);
+
+            var headers = GetNormalizedHeaders(e);
+
+            Assert.Equal(new[]
+            {
+                new KeyValuePair<string, string>("ETag", "ETag!"),
+                new KeyValuePair<string, string>("Name1", "Value1"),
+                new KeyValuePair<string, string>("Name2", "Value2-1"),
+                new KeyValuePair<string, string>("Name2", "Value2-2"),
+                new KeyValuePair<string, string>("Name3", "Value3"),
+            }, headers);
+        }
+
+        private KeyValuePair<string, string>[] GetNormalizedHeaders(Http2HeadersEnumerator enumerator)
+        {
+            var headers = new List<KeyValuePair<string, string>>();
+            while (enumerator.MoveNext())
+            {
+                headers.Add(enumerator.Current);
+            }
+            return headers.ToArray();
+        }
+    }
+}