@eluvio/elv-js-helpers/test/unit/src/Boolean/isErr.test.js

A collection of Javascript helper functions used by several Eluvio libraries.

const TH = require('../../../test-helpers')
const isErr = TH.requireSrcFile('Boolean/isErr')

describe('isErr', () => {

  const Err = TH.requireSrcFile('ADT/Err')
  const Ok = TH.requireSrcFile('ADT/Ok')

  it('should return true for Err', () => {
    isErr(Err(42)).should.be.true
  })

  it('should return false for Ok', () => {
    isErr(Ok(42)).should.be.false
  })

  it('should return false for non-Result values', () => {
    isErr(5).should.be.false
    isErr(undefined).should.be.false
    isErr(null).should.be.false
    isErr('foo').should.be.false
  })

})