Edit in JSFiddle

describe('odd', function() {
  it('returns true for an odd number', function() {
    expect(odd(37)).toBe(true);
  });
  it('returns false for an even number', function() {
    expect(odd(422)).toBe(false);
  });
  it('returns false for zero', function() {
    expect(odd(0)).toBe(false);
  });
});

function odd(n) {
  return n % 2 === 1;
}