Cover the Ruby MCP client in the smoke tests

.github/workflows/ci.yml

@@ -41,5 +41,12 @@ jobs:
         with:
           go-version: "1.25"
 
+      # 3.4 is the oldest series still supported; 3.2 reached end of life in
+      # March 2026.
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: "3.4"
+
       - name: Run smoke tests
         run: ./tests/smoke-test.sh

tests/README.md

@@ -7,9 +7,11 @@ This directory contains smoke tests for the MCP quickstart examples. These tests
 The smoke tests verify:
 
 - **Servers**: Each weather server (Python, TypeScript, Rust, Go) can start, respond to MCP protocol requests, and honour the output schemas it advertises
-- **Clients**: The Python and TypeScript MCP clients can connect to a mock server and list tools
+- **Clients**: The Python, TypeScript and Ruby MCP clients can connect to a mock server and list tools
 
-The Go and Rust clients are not covered here: on `main` both abort when no `.env` file is present, so they cannot be driven without credentials. Making them start credential-free is a change in their own directories, so their coverage lands with those changes rather than here. The Ruby examples are not covered either — the `mcp` gem cannot negotiate protocol revision `2026-07-28`.
+The Go and Rust clients are not covered here: on `main` both abort when no `.env` file is present, so they cannot be driven without credentials. Making them start credential-free is a change in their own directories, so their coverage lands with those changes rather than here.
+
+The Ruby **weather server** is not covered, for an upstream reason rather than a local one. The `mcp` gem negotiates `2026-07-28`, but its server never emits the `resultType` field that revision makes mandatory, so the test client rejects its responses — including `tools/list`. That is a fix for the gem, not something an example can work around. The Ruby **client** is covered: there it is the gem's client code that runs, and the server it is pointed at is the mock.
 
 ## Structured content
 
@@ -37,6 +39,8 @@ Tool calls reach the live NWS API. When it is unreachable the tools return an er
 - **Rust** stable
 - **Cargo** (for Rust builds)
 - **Go** 1.25+
+- **Ruby** 3.4+ (3.2 and 3.3 satisfy the gems, but 3.2 is past end of life)
+- **Bundler** (ships with Ruby 3.x)
 
 ## How It Works
 
@@ -111,6 +115,9 @@ nvm install 24
 
 # Rust
 curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
+
+# Ruby (via rbenv)
+rbenv install 3.4
 ```
 
 ## Adding New Tests

tests/smoke-test.sh

@@ -100,19 +100,32 @@ test_mcp_client_typescript() {
     node "${client_dir}/build/index.js" "${MOCK_SERVER}" >/dev/null 2>&1
 }
 
+# Test: Ruby MCP client
+test_mcp_client_ruby() {
+    check_dependency ruby || return 1
+    check_dependency bundle || return 1
+    local client_dir="${PROJECT_ROOT}/mcp-client-ruby"
+    ensure_bundled "${client_dir}" || return 1
+    (cd "${client_dir}" && bundle exec ruby client.rb "${MOCK_SERVER}") >/dev/null 2>&1
+}
+
 # Run all tests
 #
-# All four servers are covered. The Go and Rust clients are not: on main both
-# abort when no .env file is present, so they cannot be driven without
-# credentials. Making them start credential-free is a change in their own
-# directories, so their coverage lands with those changes rather than here.
+# The Go and Rust clients are not covered: on main both abort when no .env file
+# is present, so they cannot be driven without credentials. Making them start
+# credential-free is a change in their own directories, so their coverage lands
+# with those changes rather than here.
+#
+# Nor is the Ruby weather server: the mcp gem does not stamp the resultType
+# field that 2026-07-28 requires, so the test client rejects its responses.
 print_header "Running smoke tests"
 run_test "weather-server-python" test_weather_server_python
 run_test "weather-server-typescript" test_weather_server_typescript
 run_test "weather-server-rust" test_weather_server_rust
 run_test "weather-server-go" test_weather_server_go
 run_test "mcp-client-python" test_mcp_client_python
 run_test "mcp-client-typescript" test_mcp_client_typescript
+run_test "mcp-client-ruby" test_mcp_client_ruby
 
 # Print summary
 echo ""

tests/utils.sh

@@ -138,3 +138,16 @@ ensure_built() {
         run_build "go build in ${dir}" go build -o "server$(exe_suffix)" . || return 1
     fi
 }
+
+# Ensure a Ruby project directory has its gems installed.
+#
+# Unlike ensure_built there is no artefact to test for -- a Ruby example has no
+# build step and Gemfile.lock is gitignored -- so ask Bundler directly.
+ensure_bundled() {
+    local dir=$1
+    cd "${dir}" || return 1
+
+    if ! bundle check >/dev/null 2>&1; then
+        run_build "bundle install in ${dir}" bundle install || return 1
+    fi
+}