__mock__ ci-info.js

const ciInfo = jest.genMockFromModule(`ci-info`)

ciInfo.isCI = true
ciInfo.name = `bad default`

function setName(name) {
  ciInfo.name = name
}
ciInfo.setName = setName
module.exports = ciInfo

__test__ ci.js

describe(`CI detection`, () => {
  beforeEach(() => {
    jest.resetModules()
  })

  it(`Detects CI when ci-info detects one`, () => {
    const { isCI, getCIName } = require(`../ci`)
    jest.mock(`ci-info`)

    const ciInfo = require(`ci-info`)
    ciInfo.isCI = true
    ciInfo.setName(`testname`)

    expect(isCI()).toBeTruthy()
    expect(getCIName()).toEqual(`testname`)
  })
})

ci.js

const ci = require(`ci-info`)

const CI_DEFINITIONS = [
  getEnvFromCIInfo,
  getEnvDetect({ key: `NOW_BUILDER_ANNOTATE`, name: `ZEIT Now` }),
  getEnvDetect({ key: "NOW_REGION", name: "ZEIT Now v1" }),
  herokuDetect,
  envFromCIandCIName,
]
console.log(CI_DEFINITIONS)

const CIName = CI_DEFINITIONS.find(fn => {
  const res = fn()
  if (res) {
    console.log(`got res`, res)
    return res
  }
  return false
})

console.log(`CI NAME = `, CIName)

function isCI() {
  return !!CIName
}

function getCIName() {
  if (!isCI()) {
    return
  }
  console.log(`returning `, CIName)
  return CIName
}

module.exports = { isCI, getCIName }

// Helper functions
function getEnvFromCIInfo() {
  if (ci.isCI) {
    console.log(`JAMO OK returning `, ci.name)
    return ci.name || `ci-info detected w/o name`
  }
  console.log(`JAMO FAIL`)
  return false
}

function getEnvDetect({ key, name }) {
  return function() {
    console.log(`looking for ${key} in env to detect ${name}`)
    if (process.env[key]) {
      return name
    }
    return false
  }
}

function herokuDetect() {
  console.log(`looking for heroku in path to detect heroku`)
  if (/\.heroku\/node\/bin\/node/.test(process.cwd())) {
    return `Heroku`
  }
  return false
}

function envFromCIandCIName() {
  if (process.env.CI_NAME) {
    return process.env.CI_NAME
  } else if (process.env.CI) {
    return `CI detected without name`
  }
}