add tests

README.md

@@ -1 +1,3 @@
-# ProjectName
+# Timeshift
+
+TODO: docs and open-source

package.json

@@ -1,12 +1,18 @@
 {
-  "name": "@nelson/timeshift",
+  "name": "timeshift",
   "version": "0.0.0",
   "description": "Time shifting in JavaScript",
-  "author": "Nelson-ai",
+  "author": "David Hérault <dherault@nelson.ai> (https://github.com/dherault)",
   "license": "SEE LICENSE IN LICENSE",
   "main": "src/index.js",
   "scripts": {
-    "test": "echo \"Error: no test specified\" && exit 0"
+    "test": "./node_modules/.bin/mocha $npm_package_options_mocha",
+    "coverage": "./node_modules/.bin/istanbul cover _mocha -- $npm_package_options_mocha",
+    "coverage:serve": "cd coverage/lcov-report && python -m SimpleHTTPServer",
+    "coverage:all": "npm run coverage && npm run coverage:serve"
+  },
+  "options": {
+    "mocha": "--bail --check-leaks"
   },
   "repository": {
     "type": "git",

src/index.js

@@ -16,6 +16,8 @@ function timeshift(...args) {
   FakeDate.now = () => OriginalDate.now() - diff;
 
   Date = FakeDate;
+
+  return OriginalDate;
 }
 
 module.exports = timeshift;

test/index.js

@@ -0,0 +1,46 @@
+/* global it */
+const { assert } = require('chai');
+const timeshift = require('..');
+
+const OriginalDate = Date;
+
+it('travels throught time', () => {
+
+  const frenchRevolution = new Date('1789-07-14');
+
+  timeshift('1789-07-14');
+
+  // 5 ms margin error for slow machines
+  assert.approximately(new Date().getTime(), frenchRevolution.getTime(), 5);
+});
+
+it('can come back safe', () => {
+
+  timeshift();
+
+  assert.strictEqual(Date, OriginalDate);
+});
+
+// Test Date constructor with arguments after shifting
+it('knows what happended last summer', () => {
+
+  const lastSummer = new Date('2016-07-14');
+
+  // 1 hour until the new millenium, best party ever
+  timeshift('2999-12-31T23:00:00');
+
+  assert.strictEqual(new Date('2016-07-14').getTime(), lastSummer.getTime());
+
+  timeshift();
+});
+
+// Test Date.now after shifting
+it('savours the moment', () => {
+  // 1970-01-01 the begining of JavaScript time
+  timeshift(0);
+
+  // Let us witness the big bang of JavaScript
+  assert.approximately(Date.now(), 0, 5);
+
+  timeshift();
+});