Add Vitest coverage tooling and unit tests for core utils

[devin-ai-integration]

Checklist

• I have read the Contributor Guide
• I have read and agree to the Code of Conduct
• I have added a description of my changes and why I'd like them included in the section below

Description of Changes

Coverage analysis: the repo had no test runner at all (npm test was echo "Error: no test specified" && exit 1), so every module was at 0%. This adds Vitest with v8 coverage and covers the modules carrying the most untested branching logic — the src/utils helpers plus createCommand and the template selector. Overall statement coverage goes from 0% to 49%, with src/utils at 98% and src/utils/env + src/utils/git at 100%.

Tooling:

• vitest + @vitest/coverage-v8 devDependencies, vitest.config.ts, and test / test:watch / test:coverage scripts.
• Sources import each other via baseUrl-relative specifiers with .js extensions (import { log } from 'utils/logger.js'), which Node/tsup resolve but Vitest does not, so the config maps them back to the TypeScript sources:

alias: [{ find: /^(commands|types|utils)\/(.+)\.js$/, replacement: path.resolve(repoRoot, 'src/$1/$2.ts') }]

• Coverage counts src/**/*.ts and excludes src/scripts/**, COMMAND_TEMPLATE/**, _template/**, src/types/**, and test files.

Tests (38, colocated as *.test.ts): all LogLevel/LogColor branches in logger, .nextquickrc read/parse/exit paths, .env.local presence and missing-variable reporting, install-plugins merge semantics and its failing-plugin and unreadable-package.json paths, all four check-git exports including the dirty-tree prompt in both answers, setup-git-repo, check-directory, package-manager, createCommand plugin filtering, the None template path, and recursive template-copy-transfer.

Approach: fs-touching modules run against real fs.mkdtemp directories with process.cwd() stubbed, rather than mocking fs; child_process, inquirer, and open are mocked, so nothing shells out to real git/npm. process.exit is stubbed to throw a sentinel so exit paths are assertable. Assertions avoid ANSI codes so they hold in both TTY and non-TTY runs. No source files were modified.

Uncovered remainders are the command entrypoints (init, deploy, database, auth and their installer plugins) and src/index.ts, which are thin orchestration over create-next-app, npm, and interactive prompts — worth covering separately if you want them.

Related Issues

None

Link to Devin session: https://app.devin.ai/sessions/5a924e887d5f4c51ae9503d76d7715c0
Requested by: @lox-bot

[devin-ai-integration]

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