Updated the test system

test/initialize2DArray.test.js

@@ -0,0 +1,9 @@
+const expect = require('expect');
+const {initialize2DArray} = require('./_30s.js');
+
+test('initialize2DArray is a Function', () => {
+  expect(initialize2DArray).toBeInstanceOf(Function);
+});
+test('Initializes a 2D array of given width and height and value', () => {
+  expect(initialize2DArray(2, 2, 0)).toEqual([[0, 0], [0, 0]]);
+});