Updated the test system

test/isPrime.test.js

@@ -0,0 +1,9 @@
+const expect = require('expect');
+const {isPrime} = require('./_30s.js');
+
+test('isPrime is a Function', () => {
+  expect(isPrime).toBeInstanceOf(Function);
+});
+test('passed number is a prime', () => {
+  expect(isPrime(11)).toBeTruthy();
+});