JS: Instantiate for Express and add tests

javascript/ql/test/library-tests/frameworks/Express/src/middleware-flow.js

@@ -0,0 +1,43 @@
+const express = require('express');
+const app = express();
+const DB = require('@example/db');
+
+function installDb(req, res, next) {
+    req.db = new DB();
+    req.deep.db = new DB();
+    req.deep.access.db = new DB();
+    next();
+}
+
+function addMiddlewares(router) {
+    router.use(installDb);
+}
+
+function addRoutes(router) {
+    router.get('/foo', (req, res) => {
+        req.db;
+        req.deep.db;
+        req.deep.access.db;
+    });
+    let routers = {
+        '/bar': (req, res) => { req.db; },
+        '/baz': (req, res) => { req.db; },
+    };
+    for (let p in routers) {
+        router.get(p, routers[p]);
+    }
+}
+
+addMiddlewares(app);
+addRoutes(app);
+
+app.listen();
+
+
+const unrelatedApp = express();
+
+unrelatedApp.get('/', (req, res) => {
+    req.db;
+    req.deep.db;
+    req.deep.access.db;
+});