Motivation

• Add automated tests to validate the pictures API pagination behavior including the default when cursor is omitted.
• Provide a local Vitest configuration and test setup to run component and node-style API tests in a jsdom environment.
• Make component rendering deterministic in tests by mocking Next.js Image so UI tests can assert markup and interactions.

Description

• Added tests/api/pictures-route.test.ts which covers the /api/pictures route including the omitted cursor default, initial page, and final page cases.
• Added tests/components/shared/modal-pic.test.tsx which asserts ModalPic renders content and calls onClose on Escape and overlay click.
• Added tests/setup.tsx to mock next/image for the test environment and imported @testing-library/jest-dom/vitest for assertions.
• Added vitest.config.ts and updated package.json to include vitest/testing scripts and related devDependencies and scripts.

Testing

• Ran the repository linter via pnpm lint, which completed successfully as part of the pre-commit tasks.
• Could not run pnpm test/vitest in this environment because the test dependencies were not installed, so the new tests were not executed here.

Codex Task