add test

test/dig/dig.test.js

@@ -1,6 +1,32 @@
 const expect = require('expect');
 const dig = require('./dig.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);
+});