The contract between getPrefix() and prefixWord() is respected by the modules but not enforced by the specs

utils_contract_respected_but_not_enforced.js

// utils/get_prefix.js
export const getPrefix = () => 'mega';

// utils/prefix_word.js
export const prefixWord = (prefixGetter, wordToPrefix) => prefixGetter() + wordToPrefix;

// spec/utils/get_prefix_spec.js
import getPrefix from '../../utils/get_prefix';

describe('getPrefix()', => {
  it('should return mega', () =>
    expect(getPrefix).to.equal('mega'));
});

// spec/utils/prefix_word_spec.js
import sinon from 'sinon';

import prefixWord from '../../utils/prefix_word';

const getPrefix = sinon.stub().returns('mega');

describe('prefixWord()', => {
  it('should prefix the supplied word', () =>
    expect(prefixWord(getPrefix, 'Word')).to.equal('megaWord'));
});