Fix test coverage failures (#5839)

* Fix test coverage failures

* Fix test coverage failures

* Fix test coverage failures

* Fix test coverage failures

---------

Co-authored-by: christopherholland-workday <christopher.holland+evisort@workday.com>

Author: christopherholland-workday

packages/components/jest.config.js

@@ -10,6 +10,13 @@ module.exports = {
     verbose: true,
     testPathIgnorePatterns: ['/node_modules/', '/dist/'],
     moduleNameMapper: {
-        '^../../../src/(.*)$': '<rootDir>/src/$1'
+        '^../../../src/(.*)$': '<rootDir>/src/$1',
+        // @modelcontextprotocol/sdk is ESM-only (type:module, no exports map, no CJS builds).
+        // It cannot be require()'d in Jest's CJS environment and crashes the worker.
+        // The MCP core tests only exercise pure validation functions that don't
+        // use these imports, so stubbing them out is safe.
+        // Note: @langchain/core is NOT stubbed here because it ships CJS builds
+        // (e.g. tools.cjs) that Jest can require() normally.
+        '^@modelcontextprotocol/sdk/(.*)$': '<rootDir>/test/__mocks__/esm-stub.js'
     }
 }

packages/components/test/__mocks__/esm-stub.js

@@ -0,0 +1,19 @@
+/**
+ * Stub for ESM-only packages that cannot be require()'d in Jest's CJS environment.
+ *
+ * Returns a real ES6 class for every named export so that patterns like
+ *   class MCPToolkit extends BaseToolkit { ... }
+ * don't crash at module-load time, even though the class is never instantiated
+ * in these tests.
+ */
+class Stub {}
+
+module.exports = new Proxy(
+    {},
+    {
+        get: (_target, prop) => {
+            if (prop === '__esModule') return false
+            return Stub
+        }
+    }
+)