update with tests

__tests__/main.test.ts

@@ -1,3 +1,23 @@
-describe('TODO - Add a test suite', () => {
-  it('TODO - Add a test', async () => {});
+import {wait} from '../src/wait'
+import * as process from 'process'
+import * as cp from 'child_process'
+import * as path from 'path'
+
+test('throws invalid number', async() => {
+    await expect(wait('foo')).rejects.toThrow('milleseconds not a number');
 });
+
+test('wait 500 ms', async() => {
+    const start = new Date();
+    await wait(500);
+    const end = new Date();
+    var delta = Math.abs(end.getTime() - start.getTime());
+    expect(delta).toBeGreaterThan(450);
+});
+
+// shows how the runner will run a javascript action with env / stdout protocol
+test('test runs', () => {
+    process.env['INPUT_MILLISECONDS'] = '500';
+    const ip = path.join(__dirname, '..', 'lib', 'main.js');
+    console.log(cp.execSync(`node ${ip}`).toString());
+})