The document outlines a talk by Valeri Karpov on developing a REST API using Node.js and MongoDB, focusing on test-driven development (TDD). It details the application structure, schema design principles, and various components such as Mongoose for schema validation, Express for creating the API, and testing frameworks like Mocha and Superagent. Additionally, it highlights best practices in API design and offers a preview of an upcoming video course on the topic.

1. Developing a Basic REST API from
Scratch Using TDD
Valeri Karpov
NodeJS Engineer, MongoDB
www.thecodebarbarian.com
github.com/vkarpov15
@code_barbarian

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What is this talk about?
•Earlier you heard about:
– Building a basic app
– Schema design principles
•MongoDB is great for storing web/mobile app data
•So let’s build a REST API using NodeJS!
•+ learn a bit about test-driven dev with NodeJS

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Overview
•Part 1: Shopping Cart Application
– Search for products
– Add them to your cart
– Check out with Stripe
•Part 2: Using the Mongoose ODM
•Part 3: Schema Design
•Part 4: Building an API with the Express framework
•Part 5: Testing with Mocha + Superagent

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What Does the App Do?

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What Does the App Do?

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What Does the App Do?

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App Structure
•"Bad programmers worry about the code. Good
programmers worry about data structures and their
relationships." - Linus Torvalds
•3 schemas for 3 collections:
•Products
•Categories
•Users

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Schema Relationships
•Product belongs to one or more categories
•Users can have multiple products in their cart

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Part 2: Using the Mongoose ODM
•“Object document mapper” (like ORM, but for
MongoDB)
•Written for NodeJS
•Provides schema validation

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Brief Overview of NodeJS
•require()
● Async I/O

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Your First Mongoose Schema

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Using Your Schema

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Using Your Schema

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Part 3: Schema Design
•3 schemas:
– Product
– Category
– User
•Going to use mongoose to define schemas

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Product Schema

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Product Schema in Action

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Category Schema

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Category Schema Queries
•What categories are descendants of “Electronics”?
•
•What categories are children of “Non-Fiction”?
•
•What categories are ancestors of “Phones”?

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Product + Category Schemas

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Category Schema Takeaways
•Queries in MongoDB should be simple
•“Store what you query for”
•“If you need [to use the aggregation framework in
an API endpoint], you're screwed anyway, and
should fix your program.” - Linus Torvalds

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User Schema

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Principle of Least Cardinality
•Product and user = many-to-many relationship
•Don’t necessarily need a mapping table
•User won’t have 1000s of products in cart
•Can represent relationship as array in user since
one side is small
•Arrays that grow without bound are an
antipattern!

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Part 4: The Express Framework
•Most popular NodeJS web framework
•Simple, pluggable, and fast
•Great tool for building REST APIs

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Your First Express App

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Your First Express App

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Your First Express App

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What is REST?
•Representational State Transfer
•HTTP request -> JSON HTTP response
•Business logic on top of MongoDB schemas

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Structuring Your REST API

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GET /category/id/:id

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GET /category/parent/:id

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GET /product/category/:id

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Adding Products to User’s Cart
•Recall cart is an array of products

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Adding Products to User’s Cart

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PUT /me/cart Takeaways
•Mongoose lets you be lazy
•Access control using subdocs

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Bonus: Stripe Checkout

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Bonus: Stripe Checkout

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Part 4 Takeaways
•Express REST API on top of mongoose
– Access control
– Business logic
– Define what operations user can take on database
•Mongoose casting and validation for APIs

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Part 5: Test-Driven Development
•Building an API is tricky
•Lots of different error conditions
•Express has a lot of magic under the hood

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NodeJS Concurrency and Testing
•NodeJS runs in an event loop
•Single threaded
•Can run client and server on same thread!
•Test server end-to-end

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Superagent
•NodeJS HTTP client
•Isomorphic: runs in both browser and NodeJS
•Same author as Express

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Mocha
•Testing Framework for NodeJS
•Same author as Express
•BDD-style syntax

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Setting Up Category API Tests

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Testing GET /category/id/:id

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Part 5 Takeaways
•NodeJS concurrency makes testing easy
•Not just unit tests - full E2E for your REST API
•Can manipulate database and make arbitrary
HTTP requests

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•Upcoming EdX Video Course
•Looking for beta testers! Fill out survey for info
– database.mongodb.com/community-survey
•More NodeJS+MongoDB content at:
– www.thecodebarbarian.com
– Twitter: @code_barbarian
Thanks for Listening!