Additional tests and updated hide footprint to match show

test/hide.test.js

@@ -4,3 +4,9 @@ const {hide} = require('./_30s.js');
 test('hide is a Function', () => {
   expect(hide).toBeInstanceOf(Function);
 });
+test('hide hides an element', () => {
+  let el = document.createElement('div');
+  el.setAttribute('style', 'display: block;');
+  hide(el);
+  expect(el.style.display).toBe('none');
+});