Tests: more Node.js tests.

test/node/promise_handler/app.js

@@ -0,0 +1,18 @@
+#!/usr/bin/env node
+
+var fs = require('fs');
+
+require('unit-http').createServer(function (req, res) {
+    res.end();
+
+    if (req.headers['X-Write-Call']) {
+        res.writeHead(200, {'Content-Type': 'text/plain'});
+        res.write('blah');
+    }
+
+    Promise.resolve().then(() => {
+        req.on('data', (data) => {
+            fs.appendFile(data.toString(), '', function() {});
+        });
+    });
+}).listen(7080);