+
+ it('Verify once()', () => {
+ let called = 0;
+ const fn = () => ++called;
+ const onceFn = once(fn, this);
+ const result1 = onceFn();
+ expect(called).toBe(1);
+ expect(result1).toBe(1);
+ const result2 = onceFn();
+ expect(called).toBe(1);
+ expect(result2).toBe(1);
+ const result3 = onceFn();
+ expect(called).toBe(1);
+ expect(result3).toBe(1);
+ });