Add basic HTTP client support with pluggable transports

test/mcp/client/http_test.rb

@@ -0,0 +1,212 @@
+# frozen_string_literal: true
+
+require "test_helper"
+require "faraday"
+require "webmock/minitest"
+require "mcp/client/http"
+require "mcp/client/tool"
+require "mcp/client"
+
+module MCP
+  class Client
+    class HTTPTest < Minitest::Test
+      def test_raises_load_error_when_faraday_not_available
+        client = HTTP.new(url: url)
+
+        # simulate Faraday not being available
+        HTTP.any_instance.stubs(:require).with("faraday").raises(LoadError, "cannot load such file -- faraday")
+
+        error = assert_raises(LoadError) do
+          # This should immediately try to instantiate the client and fail
+          client.send_request(request: {})
+        end
+
+        assert_includes(error.message, "The 'faraday' gem is required to use the MCP client HTTP transport")
+        assert_includes(error.message, "Add it to your Gemfile: gem 'faraday', '>= 2.0'")
+      end
+
+      def test_headers_are_added_to_the_request
+        headers = { "Authorization" => "Bearer token" }
+        client = HTTP.new(url: url, headers: headers)
+
+        request = {
+          jsonrpc: "2.0",
+          id: "test_id",
+          method: "tools/list",
+        }
+
+        stub_request(:post, url)
+          .with(
+            headers: {
+              "Authorization" => "Bearer token",
+              "Content-Type" => "application/json",
+            },
+            body: request.to_json,
+          )
+          .to_return(
+            status: 200,
+            headers: { "Content-Type" => "application/json" },
+            body: { result: { tools: [] } }.to_json,
+          )
+
+        # The test passes if the request is made with the correct headers
+        # If headers are wrong, the stub_request won't match and will raise
+        client.send_request(request: request)
+      end
+
+      def test_send_request_returns_faraday_response
+        request = {
+          jsonrpc: "2.0",
+          id: "test_id",
+          method: "tools/list",
+        }
+
+        stub_request(:post, url)
+          .with(body: request.to_json)
+          .to_return(
+            status: 200,
+            headers: { "Content-Type" => "application/json" },
+            body: { result: { tools: [] } }.to_json,
+          )
+
+        response = client.send_request(request: request)
+        assert_instance_of(Hash, response)
+        assert_equal({ "result" => { "tools" => [] } }, response)
+      end
+
+      def test_send_request_raises_bad_request_error
+        request = {
+          jsonrpc: "2.0",
+          id: "test_id",
+          method: "tools/list",
+        }
+
+        stub_request(:post, url)
+          .with(body: request.to_json)
+          .to_return(status: 400)
+
+        error = assert_raises(RequestHandlerError) do
+          client.send_request(request: request)
+        end
+
+        assert_equal("The tools/list request is invalid", error.message)
+        assert_equal(:bad_request, error.error_type)
+        assert_equal({ method: "tools/list", params: nil }, error.request)
+      end
+
+      def test_send_request_raises_unauthorized_error
+        request = {
+          jsonrpc: "2.0",
+          id: "test_id",
+          method: "tools/list",
+        }
+
+        stub_request(:post, url)
+          .with(body: request.to_json)
+          .to_return(status: 401)
+
+        error = assert_raises(RequestHandlerError) do
+          client.send_request(request: request)
+        end
+
+        assert_equal("You are unauthorized to make tools/list requests", error.message)
+        assert_equal(:unauthorized, error.error_type)
+        assert_equal({ method: "tools/list", params: nil }, error.request)
+      end
+
+      def test_send_request_raises_forbidden_error
+        request = {
+          jsonrpc: "2.0",
+          id: "test_id",
+          method: "tools/list",
+        }
+
+        stub_request(:post, url)
+          .with(body: request.to_json)
+          .to_return(status: 403)
+
+        error = assert_raises(RequestHandlerError) do
+          client.send_request(request: request)
+        end
+
+        assert_equal("You are forbidden to make tools/list requests", error.message)
+        assert_equal(:forbidden, error.error_type)
+        assert_equal({ method: "tools/list", params: nil }, error.request)
+      end
+
+      def test_send_request_raises_not_found_error
+        request = {
+          jsonrpc: "2.0",
+          id: "test_id",
+          method: "tools/list",
+        }
+
+        stub_request(:post, url)
+          .with(body: request.to_json)
+          .to_return(status: 404)
+
+        error = assert_raises(RequestHandlerError) do
+          client.send_request(request: request)
+        end
+
+        assert_equal("The tools/list request is not found", error.message)
+        assert_equal(:not_found, error.error_type)
+        assert_equal({ method: "tools/list", params: nil }, error.request)
+      end
+
+      def test_send_request_raises_unprocessable_entity_error
+        request = {
+          jsonrpc: "2.0",
+          id: "test_id",
+          method: "tools/list",
+        }
+
+        stub_request(:post, url)
+          .with(body: request.to_json)
+          .to_return(status: 422)
+
+        error = assert_raises(RequestHandlerError) do
+          client.send_request(request: request)
+        end
+
+        assert_equal("The tools/list request is unprocessable", error.message)
+        assert_equal(:unprocessable_entity, error.error_type)
+        assert_equal({ method: "tools/list", params: nil }, error.request)
+      end
+
+      def test_send_request_raises_internal_error
+        request = {
+          jsonrpc: "2.0",
+          id: "test_id",
+          method: "tools/list",
+        }
+
+        stub_request(:post, url)
+          .with(body: request.to_json)
+          .to_return(status: 500)
+
+        error = assert_raises(RequestHandlerError) do
+          client.send_request(request: request)
+        end
+
+        assert_equal("Internal error handling tools/list request", error.message)
+        assert_equal(:internal_error, error.error_type)
+        assert_equal({ method: "tools/list", params: nil }, error.request)
+      end
+
+      private
+
+      def stub_request(method, url)
+        WebMock.stub_request(method, url)
+      end
+
+      def url
+        "http://example.com"
+      end
+
+      def client
+        @client ||= HTTP.new(url: url)
+      end
+    end
+  end
+end