a sample specification for a function that determines whether a given value is an integer

is-integer.spec.js

describe('isInteger', () => {
  describe('when provided an integer value', () => {
    it('should classify 5 as an integer');
    it('should classify -5 as an integer');
    it('should classify 0 as an integer');
  });
  describe('when provided a numerical value that is not an integer', () => {
    it('should classify 3.14 as not an integer');
    it('should classify -3.14 as not an integer');
    it('should classify NaN as not an integer');
  });
  describe('when provided a non-numerical value', () => {
    it('should classify null as not an integer');
    it('should classify undefined as not an integer');
    it('should classify true as not an integer');
    it('should classify false as not an integer');
    it('should classify {} as not an integer');
    it('should classify [] as not an integer');
    it('should classify '' as not an integer');
  });
});