Add unit test for WebBrowserUriTypeConverter.cs file

src/test/unit/System.Windows.Forms/System/Windows/Forms/WebBrowserUriTypeConverterTests.cs

@@ -0,0 +1,63 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Globalization;
+
+namespace System.Windows.Forms.Tests;
+
+public class WebBrowserUriTypeConverterTests
+{
+    private readonly WebBrowserUriTypeConverter _converter = new();
+
+    [Theory]
+    [InlineData("ftp.microsoft.com", "http://ftp.microsoft.com/")]
+    [InlineData("  www.example.com  ", "http://www.example.com/")]
+    [InlineData("HTTPS://secure.com", "https://secure.com/")]
+    [InlineData("localhost", "http://localhost/")]
+    [InlineData("sub.domain.com/path", "http://sub.domain.com/path")]
+    public void WebBrowserUri_ConvertFrom_RelativeUri_PrependsHttp(string input, string expected)
+    {
+        Uri result = (Uri)_converter.ConvertFrom(null, CultureInfo.InvariantCulture, input)!;
+
+        result.Should().NotBeNull();
+        result.Should().BeOfType<Uri>();
+        result.Should().Be(expected);
+    }
+
+    [Theory]
+    [InlineData("http://valid.com")]
+    [InlineData("https://secure.com")]
+    [InlineData("file:///C:/path/to/file.txt")]
+    public void WebBrowserUri_ConvertFrom_AbsoluteUri_ReturnsSame(string input)
+    {
+        Uri inputUri = new(input);
+        Uri result = (Uri)_converter.ConvertFrom(null, CultureInfo.InvariantCulture, inputUri)!;
+
+        result.Should().Be(inputUri);
+    }
+
+    [Fact]
+    public void WebBrowserUri_ConvertFrom_EmptyString_ReturnsNull()
+    {
+        object? result = _converter.ConvertFrom(null, CultureInfo.InvariantCulture, "");
+
+        result.Should().BeNull();
+    }
+
+    [Fact]
+    public void WebBrowserUri_ConvertFrom_InvalidUri_ThrowsUriFormatException()
+    {
+        Action action = () => _converter.ConvertFrom(null, CultureInfo.InvariantCulture, "http://inv@lid uri");
+
+        action.Should().Throw<UriFormatException>();
+    }
+
+    [Fact]
+    public void WebBrowserUri_ConvertFrom_AlreadyUri_ReturnsSameUri()
+    {
+        Uri uri = new("http://www.microsoft.com/");
+        Uri result = (Uri)_converter.ConvertFrom(null, CultureInfo.InvariantCulture, uri)!;
+
+        result.Should().Be(uri);
+    }
+}