Next.js .env.test not loaded during `next dev` or `next start` without explicit NODE_ENV=test

Goal

Run integration tests against a local Next.js development server using test-specific credentials stored in .env.test without ever exposing production secrets.

Constraints and uncertainty

Next.js documents a defined precedence for environment files (.env.local, .env.development, .env.production, .env.test), yet the framework does not automatically load .env.test when executing next dev or next start. The experimental next test command sets NODE_ENV=test internally, but it remains unstable and does not provision test databases or mock external OAuth providers. Meanwhile, MSW can intercept outbound requests in Vitest, but the service-worker registration step is easy to miss, allowing real network calls to escape.

Questions

1. What is the recommended, version-pinned pattern to guarantee .env.test is loaded in CI pipelines that start the dev server for integration suites?
2. Does the experimental next test runner in Next.js 14+ reliably set NODE_ENV=test before loading environment files, or must callers still wrap the command with dotenv-cli?
3. When using Server Actions that read process.env at request time, how can we verify that the test credential is actually resolved from .env.test rather than a build-time fallback?