Test README prompt usage example

Author: sambostock

README.md

@@ -429,6 +429,7 @@ e.g. around authentication state or user preferences.
 
 Register prompts with the MCP server:
 
+<!-- SNIPPET ID: prompts_usage -->
 ```ruby
 server = MCP::Server.new(
   name: "my_server",

test/fixtures/files/code_snippet_wrappers/readme/prompts_usage.rb

@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+
+require "mcp"
+
+MyPrompt = MCP::Prompt.define(
+  name: "my_prompt",
+  description: "Test prompt",
+  arguments: [
+    MCP::Prompt::Argument.new(
+      name: "message",
+      description: "Input message",
+      required: true,
+    ),
+  ],
+) do |_args, server_context:|
+  MCP::Prompt::Result.new(
+    description: "Response with user context",
+    messages: [
+      MCP::Prompt::Message.new(
+        role: "user",
+        content: MCP::Content::Text.new("User ID: #{server_context[:user_id]}"),
+      ),
+    ],
+  )
+end
+
+current_user = Object.new
+def current_user.id = 123
+
+b = binding
+eval(File.read("code_snippet.rb"), b) # rubocop:disable Security/Eval -- We need to run the snippet in this context
+server = b.local_variable_get(:server)
+
+puts server.handle_json({
+  jsonrpc: "2.0",
+  id: "1",
+  method: "prompts/get",
+  params: { name: "my_prompt", arguments: { message: "Test message" } },
+}.to_json)

test/integration/readme_code_snippets_test.rb

@@ -221,6 +221,24 @@ class ReadmeCodeSnippetsTest < ActiveSupport::TestCase
     )
   end
 
+  test "Prompt usage example works exactly as documented in README" do
+    assert_json_lines(
+      [
+        {
+          jsonrpc: "2.0",
+          id: "1",
+          result: {
+            description: "Response with user context",
+            messages: [
+              { role: "user", content: { type: "text", text: "User ID: 123" } },
+            ],
+          },
+        },
+      ],
+      run_code_snippet("prompts_usage"),
+    )
+  end
+
   private
 
   def assert_json_lines(expected, actual, message = "Expected the given JSON lines")