Updated the test system

test/runPromisesInSeries.test.js

@@ -0,0 +1,10 @@
+const expect = require('expect');
+const {runPromisesInSeries} = require('./_30s.js');
+
+test('runPromisesInSeries is a Function', () => {
+  expect(runPromisesInSeries).toBeInstanceOf(Function);
+});
+const delay = d => new Promise(r => setTimeout(r, d));
+test('Runs promises in series', () => {
+  runPromisesInSeries([() => delay(100), () => delay(200).then(() => expect(true).toBeTruthy())]);
+});