Updated the test system

test/binarySearch.test.js

@@ -0,0 +1,18 @@
+const expect = require('expect');
+const {binarySearch} = require('./_30s.js');
+
+test('binarySearch is a Function', () => {
+  expect(binarySearch).toBeInstanceOf(Function);
+});
+test('Finds item in array', () => {
+  expect(binarySearch([1, 4, 6, 7, 12, 13, 15, 18, 19, 20, 22, 24], 6)).toBe(2);
+});
+test('Returns -1 when not found', () => {
+  expect(binarySearch([1, 4, 6, 7, 12, 13, 15, 18, 19, 20, 22, 24], 21)).toBe(-1);
+});
+test('Works with empty arrays', () => {
+  expect(binarySearch([], 21)).toBe(-1);
+});
+test('Works for one element arrays', () => {
+  expect(binarySearch([1], 1)).toBe(0);
+});