Test README prompts instrumentation callback example

Author: sambostock

README.md

@@ -448,6 +448,7 @@ The server will handle prompt listing and execution through the MCP protocol met
 The server allows registering a callback to receive information about instrumentation.
 To register a handler pass a proc/lambda to as `instrumentation_callback` into the server constructor.
 
+<!-- SNIPPET ID: prompts_instrumentation_callback -->
 ```ruby
 MCP.configure do |config|
   config.instrumentation_callback = ->(data) {

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

@@ -0,0 +1,6 @@
+# frozen_string_literal: true
+
+require "mcp"
+require_relative "code_snippet"
+
+puts MCP::Server.new.handle_json({ jsonrpc: "2.0", id: "1", method: "ping" }.to_json)

test/integration/readme_code_snippets_test.rb

@@ -239,6 +239,15 @@ class ReadmeCodeSnippetsTest < ActiveSupport::TestCase
     )
   end
 
+  test "Prompts Instrumentation Callback example works exactly as documented in README" do
+    stdout = run_code_snippet("prompts_instrumentation_callback")
+
+    assert_equal(<<~STDOUT, stdout)
+      Got instrumentation data {method: "ping", duration: 1.23}
+      #{{ jsonrpc: "2.0", id: "1", result: {} }.to_json}
+    STDOUT
+  end
+
   private
 
   def assert_json_lines(expected, actual, message = "Expected the given JSON lines")