@eluvio/elv-js-helpers/test/unit/src/ADT/Err.test.js

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

const TH = require('../../../test-helpers')
const Err = TH.requireSrcFile('ADT/Err')

describe('Err', () => {

  const curry = TH.requireSrcFile('Functional/curry')
  const liftA2 = TH.requireSrcFile('Functional/liftA2')
  const kind = TH.requireSrcFile('Validation/kind')
  const Ok = TH.requireSrcFile('ADT/Ok')
  const resultUnwrap = TH.requireSrcFile('Conversion/resultUnwrap')

  const okObject = Ok(42)
  const errObject1 = Err('failed to obtain first input')
  const errObject2 = Err(['failed to obtain second input'])
  const mult = (a, b) => a * b
  const multResults = liftA2(curry(mult))

  it('should create an instance of ADT that works as expected with a lifted function', () => {
    multResults(errObject1, okObject).inspect().should.equal('Err [ "failed to obtain first input" ]')
    multResults(okObject, errObject2).inspect().should.equal('Err [ "failed to obtain second input" ]')
    multResults(errObject1, errObject2).inspect().should.equal('Err [ "failed to obtain first input", "failed to obtain second input" ]')
  })

  it('should automatically wrap non-array value in an array', () => {
    kind(resultUnwrap(errObject1)).should.equal('Array')
  })

  it('should be able to wrap an object', () => {
    const structuredErr = Err({message: 'foo', err: TypeError})
    kind(resultUnwrap(structuredErr)).should.equal('Array')
    resultUnwrap(structuredErr)[0].message.should.equal('foo')
  })

  it('should throw an exception only for empty array', () => {
    TH.expect(()=> Err([])).to.throw('Err cannot wrap an empty array')
    TH.expect(()=> Err([undefined])).to.not.throw
  })
})