Add unit test suite for app components and Amplify configuration

[bigweavergammainternal]

This pull request was generated by @kiro-agent 👻

Comment with /kiro fix to address specific feedback or /kiro all to address everything.
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Problem

The project had no test framework or test files configured, leaving all source code without automated test coverage. This created a gap in quality assurance for the Next.js App Router components and AWS Amplify Gen 2 backend configuration.

Solution

Set up a zero-dependency testing framework using Node.js built-in test runner (node:test) with a custom TypeScript loader, and added comprehensive unit tests across all key source files.

Testing Framework Setup

• Test runner: Node.js built-in node:test module — no additional test dependencies required
• TypeScript support: Custom __tests__/helpers/ts-loader.js that strips TypeScript syntax, converts ESM imports/exports to CJS, and resolves @/ path aliases
• Mock system: Built-in mock module registration via Module._load override, enabling isolation of AWS Amplify dependencies
• Test script: Added npm test command to package.json using node --test with auto-discovery of *.test.js files

Test Coverage (40 tests total)

app/page.tsx — App component (20 tests)

• Verifies client component directive and default export
• Validates todo list UI rendering (heading, button, list element, success message, tutorial link)
• Tests createTodo function interaction (prompt call, button wiring, Todo.create invocation)
• Validates data subscription flow (useState, observeQuery, useEffect mount, list rendering, state updates)
• Confirms AWS Amplify integration (generateClient import, Schema type, Amplify.configure, typed client)

app/layout.tsx — RootLayout component (9 tests)

• Validates metadata exports (title, description, Metadata type)
• Tests component structure (default export, children prop, body rendering)
• Verifies HTML attributes (lang="en") and Inter font usage

amplify/auth/resource.ts — Auth configuration (3 tests)

• Verifies defineAuth is called to configure authentication
• Confirms email is set as the login mechanism
• Validates the auth configuration is exported

amplify/data/resource.ts — Data schema (8 tests)

• Verifies schema defines a Todo model with a content string field
• Tests authorization setup on the Todo model
• Confirms defineData is called with apiKey as default authorization mode
• Validates API key expiration is set to 30 days

Files Added/Modified

File	Description
__tests__/helpers/ts-loader.js	TypeScript loader with mock registration for node:test
__tests__/app/page.test.js	Unit tests for the main App component
__tests__/app/layout.test.js	Unit tests for the RootLayout component
__tests__/amplify/auth/resource.test.js	Unit tests for Amplify auth configuration
__tests__/amplify/data/resource.test.js	Unit tests for Amplify data schema
package.json	Added test script

Testing

• All 40 tests pass when running npm test
• Tests execute using Node.js built-in test runner with no additional dependencies
• AWS Amplify modules (@aws-amplify/backend, aws-amplify/data) are fully mocked to isolate component behavior from cloud services