next.js/test/lib/turbo.ts

let loggedTurbopack = false

/**
 * Utility function to determine if a given test case needs to run with --turbo.
 *
 * This is primarily for the gradual test enablement with latest turbopack upstream changes.
 *
 * Note: it could be possible to dynamically create test cases itself (createDevTest(): it.each([...])), but
 * it makes hard to conform with existing lint rules. Instead, starting off from manual fixture setup and
 * update test cases accordingly as turbopack changes enable more test cases.
 */
export function shouldRunTurboDevTest(): boolean {
  if (!!process.env.NEXT_TEST_WASM) {
    return false
  }

  const shouldRunTurboDev = !!process.env.IS_TURBOPACK_TEST
  if (shouldRunTurboDev && !loggedTurbopack) {
    require('console').log(
      `Running tests with turbopack because environment variable TURBOPACK is set`
    )
    loggedTurbopack = true
  }

  return shouldRunTurboDev
}

export function getTurbopackFlag(): string {
  if (!!process.env.IS_TURBOPACK_TEST) {
    return '--turbo'
  } else {
    throw Error(`Cannot get the flag for running turbopack`)
  }
}