Updated the test system

test/randomIntArrayInRange.test.js

@@ -0,0 +1,18 @@
+const expect = require('expect');
+const {randomIntArrayInRange} = require('./_30s.js');
+
+test('randomIntArrayInRange is a Function', () => {
+  expect(randomIntArrayInRange).toBeInstanceOf(Function);
+});
+const lowerLimit = Math.floor(Math.random() * 20);
+const upperLimit = Math.floor(lowerLimit + Math.random() * 10);
+const arr = randomIntArrayInRange(lowerLimit, upperLimit, 10);
+test('The returned array contains only integers', () => {
+  expect(arr.every(x => typeof x === 'number')).toBeTruthy();
+});
+test('The returned array has the proper length', () => {
+  expect(arr.length).toBe(10);
+});
+test("The returned array's values lie between provided lowerLimit and upperLimit (both inclusive).", () => {
+  expect(arr.every(x => x >= lowerLimit && x <= upperLimit)).toBeTruthy();
+});