text: import { expect } from 'chai';
  import isString from './is-string';
  
  describe('#isString()', () => {
    it('should return false if undefined is passed', () => {
      expect(isString()).to.equal(false);
    });
  
    it('should return false if null is passed', () => {
      expect(isString(null)).to.equal(false);
    });
  
    it('should return false if a plain object is passed', () => {
      expect(isString({})).to.equal(false);
    });
  
    it('should return false if number is passed', () => {
      expect(isString(2)).to.equal(false);
    });
  
    it('should return true if string is passed', () => {
      expect(isString('foo')).to.equal(true);
    });
  });
  