Updated the test system

test/dig.test.js

@@ -0,0 +1,32 @@
+const expect = require('expect');
+const {dig} = require('./_30s.js');
+
+const data = {
+  level1: {
+    level2: {
+      level3: 'some data',
+      level3f: false,
+      level3a: [1, 2, 3, 4]
+    }
+  }
+};
+
+test('dig is a Function', () => {
+  expect(dig).toBeInstanceOf(Function);
+});
+
+test('Dig target success', () => {
+  expect(dig(data, 'level3')).toEqual('some data');
+});
+
+test('Dig target with falsey value', () => {
+  expect(dig(data, 'level3f')).toEqual(false);
+});
+
+test('Dig target with array', () => {
+  expect(dig(data, 'level3a')).toEqual([1, 2, 3, 4]);
+});
+
+test('Unknown target return undefined', () => {
+  expect(dig(data, 'level4')).toEqual(undefined);
+});