Updated the test system

test/shank.test.js

@@ -0,0 +1,22 @@
+const expect = require("expect");
+const {shank} = require("./_30s.js");
+
+test("shank is a Function", () => {
+  expect(shank).toBeInstanceOf(Function);
+});
+
+const names = ['alpha', 'bravo', 'charlie'];
+
+test("Returns an array with the added elements.", () => {
+  expect(shank(names, 1, 0, 'delta')).toEqual(['alpha', 'delta', 'bravo', 'charlie']);
+});
+
+test("Returns an array with the removed elements.", () => {
+  expect(shank(names, 1, 1)).toEqual(['alpha', 'charlie']);
+});
+
+test("Does not mutate the original array", () => {
+  shank(names, 1, 0, 'delta');
+  expect(names).toEqual(['alpha', 'bravo', 'charlie']);
+});
+