Updated the test system

test/lcm.test.js

@@ -0,0 +1,12 @@
+const expect = require('expect');
+const {lcm} = require('./_30s.js');
+
+test('lcm is a Function', () => {
+  expect(lcm).toBeInstanceOf(Function);
+});
+test('Returns the least common multiple of two or more numbers.', () => {
+  expect(lcm(12, 7)).toBe(84);
+});
+test('Returns the least common multiple of two or more numbers.', () => {
+  expect(lcm(...[1, 3, 4, 5])).toBe(60);
+});