Updated the test system

test/sortedIndex.test.js

@@ -0,0 +1,12 @@
+const expect = require('expect');
+const {sortedIndex} = require('./_30s.js');
+
+test('sortedIndex is a Function', () => {
+  expect(sortedIndex).toBeInstanceOf(Function);
+});
+test('Returns the lowest index at which value should be inserted into array in order to maintain its sort order.', () => {
+  expect(sortedIndex([5, 3, 2, 1], 4)).toBe(1);
+});
+test('Returns the lowest index at which value should be inserted into array in order to maintain its sort order.', () => {
+  expect(sortedIndex([30, 50], 40)).toBe(1);
+});