Add Theme property assertions to client-server integration tests

Co-authored-by: jozkee <16040868+jozkee@users.noreply.github.com>

Author: Copilot

tests/ModelContextProtocol.Tests/Client/McpClientTests.cs

@@ -37,8 +37,8 @@ protected override void ConfigureServices(ServiceCollection services, IMcpServer
                 WebsiteUrl = "https://example.com",
                 Icons =
                 [
-                    new Icon { Source = "https://example.com/icon-48.png", MimeType = "image/png", Sizes = ["48x48"] },
-                    new Icon { Source = "https://example.com/icon.svg", MimeType = "image/svg+xml", Sizes = ["any"] }
+                    new Icon { Source = "https://example.com/icon-48.png", MimeType = "image/png", Sizes = ["48x48"], Theme = "light" },
+                    new Icon { Source = "https://example.com/icon.svg", MimeType = "image/svg+xml", Sizes = ["any"], Theme = "dark" }
                 ]
             };
         });
@@ -59,10 +59,12 @@ public async Task CanReadServerInfo()
         Assert.Equal("https://example.com/icon-48.png", serverInfo.Icons[0].Source);
         Assert.Equal("image/png", serverInfo.Icons[0].MimeType);
         Assert.Single(serverInfo.Icons[0].Sizes, "48x48");
+        Assert.Equal("light", serverInfo.Icons[0].Theme);
 
         Assert.Equal("https://example.com/icon.svg", serverInfo.Icons[1].Source);
         Assert.Equal("image/svg+xml", serverInfo.Icons[1].MimeType);
         Assert.Single(serverInfo.Icons[1].Sizes, "any");
+        Assert.Equal("dark", serverInfo.Icons[1].Theme);
     }
 
     [Theory]

tests/ModelContextProtocol.Tests/Configuration/McpServerBuilderExtensionsPromptsTests.cs

@@ -180,7 +180,9 @@ public async Task AttributeProperties_Propagated()
 
         Assert.NotNull(prompt.ProtocolPrompt.Icons);
         Assert.NotEmpty(prompt.ProtocolPrompt.Icons);
-        Assert.Equal("https://example.com/prompt-icon.svg", prompt.ProtocolPrompt.Icons[0].Source);
+        var icon = Assert.Single(prompt.ProtocolPrompt.Icons);
+        Assert.Equal("https://example.com/prompt-icon.svg", icon.Source);
+        Assert.Null(icon.Theme);
     }
 
     [Fact]

tests/ModelContextProtocol.Tests/Configuration/McpServerBuilderExtensionsResourcesTests.cs

@@ -213,7 +213,9 @@ public async Task AttributeProperties_Propagated()
 
         Assert.NotNull(resource.ProtocolResource.Icons);
         Assert.NotEmpty(resource.ProtocolResource.Icons);
-        Assert.Equal("https://example.com/direct-resource-icon.svg", resource.ProtocolResource.Icons[0].Source);
+        var resourceIcon = Assert.Single(resource.ProtocolResource.Icons);
+        Assert.Equal("https://example.com/direct-resource-icon.svg", resourceIcon.Source);
+        Assert.Null(resourceIcon.Theme);
 
         var resourceTemplates = await client.ListResourceTemplatesAsync(cancellationToken: TestContext.Current.CancellationToken);
         Assert.NotNull(resourceTemplates);
@@ -223,7 +225,9 @@ public async Task AttributeProperties_Propagated()
 
         Assert.NotNull(resourceTemplate.ProtocolResourceTemplate.Icons);
         Assert.NotEmpty(resourceTemplate.ProtocolResourceTemplate.Icons);
-        Assert.Equal("https://example.com/templated-resource-icon.svg", resourceTemplate.ProtocolResourceTemplate.Icons[0].Source);
+        var templateIcon = Assert.Single(resourceTemplate.ProtocolResourceTemplate.Icons);
+        Assert.Equal("https://example.com/templated-resource-icon.svg", templateIcon.Source);
+        Assert.Null(templateIcon.Theme);
     }
 
     [Fact]

tests/ModelContextProtocol.Tests/Configuration/McpServerBuilderExtensionsToolsTests.cs

@@ -646,7 +646,9 @@ public async Task AttributeProperties_Propagated()
 
         Assert.NotNull(tool.ProtocolTool.Icons);
         Assert.NotEmpty(tool.ProtocolTool.Icons);
-        Assert.Equal("https://example.com/tool-icon.svg", tool.ProtocolTool.Icons[0].Source);
+        var icon = Assert.Single(tool.ProtocolTool.Icons);
+        Assert.Equal("https://example.com/tool-icon.svg", icon.Source);
+        Assert.Null(icon.Theme);
     }
 
     [Fact]