Updated the test system

test/drop.test.js

@@ -0,0 +1,15 @@
+const expect = require('expect');
+const {drop} = require('./_30s.js');
+
+test('drop is a Function', () => {
+  expect(drop).toBeInstanceOf(Function);
+});
+test('Works without the last argument', () => {
+  expect(drop([1, 2, 3])).toEqual([2, 3]);
+});
+test('Removes appropriate element count as specified', () => {
+  expect(drop([1, 2, 3], 2)).toEqual([3]);
+});
+test('Empties array given a count greater than length', () => {
+  expect(drop([1, 2, 3], 42)).toEqual([]);
+});