Updated the test system

test/longestItem.test.js

@@ -0,0 +1,32 @@
+const expect = require('expect');
+const {longestItem} = require('./_30s.js');
+
+test('longestItem is a Function', () => {
+  expect(longestItem).toBeInstanceOf(Function);
+});
+test('Returns the longest object from plain values', () => {
+  expect(longestItem('this', 'is', 'a', 'testcase')).toEqual('testcase');
+});
+test('Returns the longest object from a spread array', () => {
+  expect(longestItem(...['a', 'ab', 'abc'])).toEqual('abc');
+});
+test('Returns the longest object from mixed input', () => {
+  expect(longestItem(...['a', 'ab', 'abc'], 'abcd')).toEqual('abcd');
+});
+test('Returns the longest array', () => {
+  expect(longestItem([1, 2, 3], [1, 2], [1, 2, 3, 4, 5])).toEqual([1, 2, 3, 4, 5]);
+});
+test('Returns the longest object when comparing arrays and strings', () => {
+  expect(longestItem([1, 2, 3], 'foobar')).toEqual('foobar');
+});
+test('Returns undefined without any input', () => {
+  expect(longestItem()).toEqual(undefined);
+});
+test('Returns first found of all similar', () => {
+  expect(longestItem('a', 'b', 'c')).toEqual('a');
+});
+test('Throws TypeError if all inputs are undefined', () => {
+  expect(() => {
+    longestItem(undefined, undefined);
+  }).toThrow(TypeError);
+});