Updated the test system

test/initial.test.js

@@ -0,0 +1,9 @@
+const expect = require('expect');
+const {initial} = require('./_30s.js');
+
+test('initial is a Function', () => {
+  expect(initial).toBeInstanceOf(Function);
+});
+test('Returns all the elements of an array except the last one', () => {
+  expect(initial([1, 2, 3])).toEqual([1, 2]);
+});