Additional tests

test/throttle.test.js

@@ -4,3 +4,8 @@ const {throttle} = require('./_30s.js');
 test('throttle is a Function', () => {
   expect(throttle).toBeInstanceOf(Function);
 });
+test('throttle returns a function', () => {
+  let throttled = throttle(x => x, 100000);
+  expect(throttled).toBeInstanceOf(Function);
+  expect(throttled(10)).toBe(undefined);
+});