Updated the test system

test/hashNode.test.js

@@ -0,0 +1,11 @@
+const expect = require('expect');
+const {hashNode} = require('./_30s.js');
+
+test('hashNode is a Function', () => {
+  expect(hashNode).toBeInstanceOf(Function);
+});
+test('Produces the appropriate hash', () => {
+  hashNode(JSON.stringify({ a: 'a', b: [1, 2, 3, 4], foo: { c: 'bar' } })).then(v =>
+    expect(v).toBe('04aa106279f5977f59f9067fa9712afc4aedc6f5862a8defc34552d8c7206393')
+  );
+});