Return a basic error message when DB connection is lost

server/middleware/dbCheck.js

@@ -0,0 +1,13 @@
+import mongoose from 'mongoose';
+import config from '../config.js';
+
+export default (req, res, next)=>{
+	// Bypass DB checks during testing
+	if(config.get('node_env') == 'test') return next();
+
+	if(mongoose.connection.readyState == 1) return next();
+	return res.status(503).send({
+		message : 'Unable to connect to database',
+		state   : mongoose.connection.readyState
+	});
+};

server/middleware/dbCheck.spec.js

@@ -0,0 +1,63 @@
+import mongoose from 'mongoose';
+import dbCheck from './dbCheck.js';
+import config from '../config.js';
+
+describe('database check middleware', ()=>{
+	let request;
+	let response;
+	let next;
+
+	beforeEach(()=>{
+		request = {
+			get : function(key) {
+				return this[key];
+			}
+		};
+		response = {
+			status : jest.fn(()=>response),
+			send   : jest.fn(()=>{})
+		};
+		next = jest.fn();
+
+		// Mock the Config module
+		jest.mock('../config.js');
+		config.get = jest.fn((param)=>{
+			// The requested key name will be reflected to the output
+			return param;
+		});
+	});
+
+	afterEach(()=>{
+		jest.clearAllMocks();
+	});
+
+	it('should return 503 if readystate != 1', ()=>{
+		const dbState = mongoose.connection.readyState;
+
+		mongoose.connection.readyState = 99;
+
+		dbCheck(request, response);
+
+		mongoose.connection.readyState = dbState;
+
+		expect(response.status).toHaveBeenLastCalledWith(503);
+		expect(response.send).toHaveBeenLastCalledWith(
+			expect.objectContaining({
+				message : 'Unable to connect to database',
+				state   : 99
+			})
+		);
+	});
+
+	it('should call next if readystate == 1', ()=>{
+		const dbState = mongoose.connection.readyState;
+
+		mongoose.connection.readyState = 1;
+
+		dbCheck(request, response, next);
+
+		mongoose.connection.readyState = dbState;
+
+		expect(next).toHaveBeenCalled();
+	});
+});