Updated the test system

test/isBoolean.test.js

@@ -0,0 +1,12 @@
+const expect = require('expect');
+const {isBoolean} = require('./_30s.js');
+
+test('isBoolean is a Function', () => {
+  expect(isBoolean).toBeInstanceOf(Function);
+});
+test('passed value is not a boolean', () => {
+  expect(isBoolean(null)).toBeFalsy();
+});
+test('passed value is not a boolean', () => {
+  expect(isBoolean(false)).toBeTruthy();
+});