Learn Mocha, Neo4j and Sequelize

In this course we will learn some of the basics of getting data into and out of Neo4J, as well as touch on some of the libraries and tooling available in the Neo4J community ecosystem, which we will leverage to quickly create and use a full-featured GraphQL API.

We will start by learning how to run and interact with Neo4J locally. Then we will develop a graph model in which to store the data that we pull from SWAPI via REST. We will then create an Apollo GraphQL API driven by a few simple schemas which fit into this model. We will then write some simple code to crawl SWAPI and insert the data into Neo4J through our GraphQL API. Once there is data in the store, we will learn about some of the features in `neo4j-graphql-js` that make connecting and accessing our graph Nodes easier.

Neo4j delivers the lightning-fast read and write performance you need. Neo4j combines native graph storage, scalable architecture optimized for speed, and ACID compliance to ensure predictability of relationship-based queries.

neo4j

Build a Neo4J & GraphQL API

Mocha is a feature-rich JavaScript test framework running on Node.js and in the browser, making asynchronous testing simple and fun. Mocha tests run serially, allowing for flexible and accurate reporting, while mapping uncaught exceptions to the correct test cases.

mocha

Every dependable library needs to have tests to ensure that you don't push accidental bugs. In this lesson, see how you can set up mocha and chai to start testing your library.

Setting up Unit Testing with Mocha and Chai

Now that you've got everything set up with mocha and chai, it's time to actually write tests. In this lesson you'll learn how to use `describe` and `it` to outline your tests and make sure you don't break your library in the future.

Unit Testing with Mocha and Chai

Mocha is a testing framework that provides structure for unit tests. In this lesson, we will be setting up Mocha with npm and npm scripts, writing a "Hello World" unit test, then writing the code to make the test pass (as an example of Test Driven Development (TDD), with the "red-green-refactor" workflow).

JavaScript Testing Fundamentals: Hello world unit test with Mocha (in ES6)

Sequelize is a promise-based ORM for Node.js and io.js. It supports the dialects PostgreSQL, MySQL, MariaDB, SQLite and MSSQL and features solid transaction support, relations, read replication and more.

sequelize

Sequelize attribute getters and setters are a convenient way to encapsulate extra logic for model properties. In this video, we'll cover adding getters and setters to enhance and even virtualize a column.

Sequelize: Getters, Setters and Virtual Columns

In this lesson, we will use Chai's request method to test our Node application's API responses.
By the end of this lesson, you will know how to:
- install the prerequisites to use mocha and chai in your application
- test for HTTP status response codes
- test for a string of text on a page
- test for a json response and validate the properties of the object
- write tests that not only verify the response of your application, but the behavior as well


Test Node RESTful API with Mocha and Chai

Chai is a BDD / TDD assertion library for node and the browser that can be delightfully paired with any javascript testing framework.

chai

Writing great ES6 style Promises for Node.js is only half the battle. Your great modules must include tests as well to ensure future iterations don't break them. In this lesson, I show you a simple ES6 Promise in Node.js, then walk you through creating tests in Mocha using chai and chai-as-promised to test both resolve and reject methods.

Testing ES6 Promises in Node.js using Mocha and Chai

Models in the Node.js ORM, Sequelize, can be expanded with both class level and instance level functions. This video will show you how to extend your models to add helpers or business logic, and explain the methods execution scope.

Sequelize: Class & Instance Methods

In this lesson, you will learn how to verify your API server is returning HTTP 400 responses when clients submit incorrect data. Returning HTTP 400 ensures that your clients are notified of the incorrect usage. Testing for them ensures your API returns errors instead of incorrect responses when supplied with incorrect data.

Test for HTTP 400 responses with Mocha and Chai

Javascript and database systems tend to be at odds with regard to how tables and columns should be named. Sequlize provides all the tools necessary to satisfy naming conventions in both your Node.js code and in your SQL database.

Sequelize: Model & Column Casing

Unit testing functions that invoke callbacks can require a lot of setup code. Using `sinon.spy` to create a fake callback function can simplify your unit tests while still allowing you to observe the output of the function you're testing.

Unit Test a Function that Invokes a Callback with a Sinon Spy

When testing functions that make HTTP requests, it's not preferable for those requests to actually run. Using the `nock` JavaScript library, we can mock out HTTP requests so that they don't actually happen, control the responses from those requests, and assert when requests are made.

Mock an HTTP request using Nock while unit testing

When mocking a JavaScript function during a unit test, it can be helpful to force a mock function to return a value of your choosing. This allows you to verify that functions you're testing will behave correctly for every possible use case.

Much like [`sinon.spy()`](https://sinonjs.org/releases/v7.0.0/spies/), [`sinon.stub()`](https://sinonjs.org/releases/v7.0.0/stubs/) creates a mock function that prevents a real function from running. But, unlike `spy`, it also allows you to declare what value you'd like the mock function to return.

Mock a function's return value using a Sinon stub

Node.js is a platform built on Chrome's JavaScript runtime for easily building fast, scalable network applications. Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient, perfect for data-intensive real-time applications that run across distributed devices.

node

Sometimes when writing a unit test, you know that the module you're testing imports a module that you would like to observe, or at the very least mock to prevent side effects like network activity or file system operations.

For JavaScript unit tests that run in Node, we can hijack the built-in `require` function by using the [`proxyquire`](https://www.npmjs.com/package/proxyquire) module, which allows us to mock one or more modules that are second-class dependencies in our unit test, replacing them with whatever we want.

This means we could replace functions with [no-ops](https://en.wikipedia.org/wiki/NOP_%28code%29) to prevent side effects, or replace them with [Sinon spies](https://egghead.io/lessons/mocha-unit-test-a-function-that-invokes-a-callback-with-a-sinon-spy) to observe the inner workings of the module you're testing.

In this video, we'll demonstrate the basics of using Proxyquire to prevent and observe a file system operation.

Mock a Node module's dependencies using Proxyquire

There are different types of data in Neo4J: Nodes and Relationships. We will cover the ways to create each type of data: creating nodes with properties, creating nodes with relationships, and creating constraints on nodes and relationships.

Create Nodes and Relationships in Neo4J with Cypher

Once there is data in Neo4J, we need to be able to access it. We will cover the structure of a cypher query to return parts of our graph.

Read Nodes and Relationships in Neo4J with Cypher

The data in our graph is unlikely to stay the same forever. We will cover the syntax used to find and modify existing data in different ways through the use of parameters.

Update Nodes and Relationships in Neo4J with Cypher

Nothing lives forever, so we need to know how to use DELETE and DETACH to get rid of nodes and relationships we no longer want in our graph.

Delete Nodes and Relationships in Neo4J with Cypher

We will learn about `neo4j-graphql-js` and how to leverage it to quickly create a full-featured API backed by Neo4J. We will create a few simple schemas to represent our model.

Use neo4j-graphql-js to Create a Simple API

We will learn to use the `@relation` directive provided by `neo4j-graphql-js` to make the relationships in our model explicit in our schemas.

Explicitly Model Schema Relationships with the @relation Directive in neo4j-graphql-js

We will use automatically generated mutations in a Apollo GraphQL API augmented with `neo4j-graphql-js` to insert data that we get from SWAPI into Neo4J.

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