Add back UrlDecoderTests

Author: Andrew Hall

src/Razor/test/Microsoft.CodeAnalysis.Razor.Workspaces.Test/Utilities/UrlDecoderTests.cs

@@ -0,0 +1,40 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the MIT license. See License.txt in the project root for license information.
+
+using System.Collections.Generic;
+using Microsoft.AspNetCore.Razor.Test.Common;
+using Microsoft.AspNetCore.Razor.Utilities;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace Microsoft.CodeAnalysis.Razor.Workspaces.Test.Utilities;
+
+public class UrlDecoderTests(ITestOutputHelper testOutput) : ToolingTestBase(testOutput)
+{
+    public static IEnumerable<object[]> UrlDecodeData =>
+        new[]
+        {
+            new object[] { "http://127.0.0.1:8080/appDir/page.aspx?foo=bar", "http://127.0.0.1:8080/appDir/page.aspx?foo=b%61r" },
+            new object[] { "http://127.0.0.1:8080/appDir/page.aspx?foo=b%ar", "http://127.0.0.1:8080/appDir/page.aspx?foo=b%%61r" },
+            new object[] { "http://127.0.0.1:8080/app%Dir/page.aspx?foo=b%ar", "http://127.0.0.1:8080/app%Dir/page.aspx?foo=b%%61r" },
+            new object[] { "http://127.0.0.1:8080/app%%Dir/page.aspx?foo=b%%r", "http://127.0.0.1:8080/app%%Dir/page.aspx?foo=b%%r" },
+            new object[] { "http://127.0.0.1:8080/appDir/page.aspx?foo=ba%r", "http://127.0.0.1:8080/appDir/page.aspx?foo=b%61%r" },
+            new object[] { "http://127.0.0.1:8080/appDir/page.aspx?foo=bar baz", "http://127.0.0.1:8080/appDir/page.aspx?foo=bar+baz" },
+            new object[] { "http://example.net/\U00010000", "http://example.net/\U00010000" },
+            new object[] { "http://example.net/\uD800", "http://example.net/\uD800" },
+            new object[] { "http://example.net/\uD800a", "http://example.net/\uD800a" },
+            // The "Baz" portion of "http://example.net/Baz" has been double-encoded - one iteration of UrlDecode() should produce a once-encoded string.
+            new object[] { "http://example.net/%6A%6B%6C", "http://example.net/%256A%256B%256C"},
+            // The second iteration should return the original string
+            new object[] { "http://example.net/jkl", "http://example.net/%6A%6B%6C"},
+            // This example uses lowercase hex characters
+            new object[] { "http://example.net/jkl", "http://example.net/%6a%6b%6c"}
+        };
+
+    [Theory]
+    [MemberData(nameof(UrlDecodeData))]
+    public void Decode(string decoded, string encoded)
+    {
+        Assert.Equal(UrlDecoder.Decode(encoded), decoded);
+    }
+}