Updated the test system

test/functionName.test.js

@@ -0,0 +1,20 @@
+const expect = require('expect');
+let output = '';
+const functionName = fn => fn.name;
+
+test('functionName is a Function', () => {
+  expect(functionName).toBeInstanceOf(Function);
+});
+test('Works for native functions', () => {
+  expect(functionName(Math.max)).toBe('max');
+});
+function fun(x) {
+  return x;
+}
+test('Works for functions', () => {
+  expect(functionName(fun)).toBe('fun');
+});
+const fn = x => x;
+test('Works for arrow functions', () => {
+  expect(functionName(fn)).toBe('fn');
+});