Testing Apollo Client/Server Applications

Following up on the GraphQL, Node.JS and React Monorepo Starter Kit and GraphQL Apollo Starter Kit (Lerna, Node.js), I have now created an extended example which includes facilities to run unit and integration tests using Jest.

The code can be found on GitHub:

apollo-client-server-tests

The following tests are included:

React Component Test

This tests asserts a react component is rendered correctly. Backend data from GraphQL is supplied via a mock [packages/client-components/src/Books/Books.test.js]

import React from 'react';
import Books from './Books';

import renderer from 'react-test-renderer'
import { MockedProvider } from 'react-apollo/test-utils';

import GET_BOOK_TITLES from './graphql/queries/booktitles';

import wait from 'waait';

const mocks = [
  {
    request: {
      query: GET_BOOK_TITLES
    },
    result: {
      data: {
        books: [
          {
            title: 'Harry Potter and the Chamber of Secrets',
            author: 'J.K. Rowling',
          },
          {
            title: 'Jurassic Park',
            author: 'Michael Crichton',
          }
        ]
      },
    },
  },
];

it('Renders one book', async () => {

  const component = renderer.create(<MockedProvider mocks={mocks} addTypename={false}>
    <Books />
  </MockedProvider>);
  expect(component.toJSON()).toEqual('Loading...');

  // to wait for event loop to complete - after which component should be loaded
  await wait(0);

  const pre = component.root.findByType('pre');
  expect(pre.children).toContain('Harry Potter and the Chamber of Secrets');

});

GraphQL Schema Test

Based on the article Extensive GraphQL Testing in 3 minutes, this test verifies the GraphQL schema is defined correctly for running the relevant queries [packages/server-books/src/schema/index.test.js].

import {
    makeExecutableSchema,
    addMockFunctionsToSchema,
    mockServer
} from 'graphql-tools';

import { graphql } from 'graphql';

import booksSchema from './index';

const titleTestCase = {
    id: 'Query Title',
    query: `
      query {
        books {
            title
        }
      }
    `,
    variables: {},
    context: {},
    expected: { data: { books: [{ title: 'Title'} , { title: 'Title' }] } }
};

const cases = [titleTestCase];

describe('Schema', () => {
    const typeDefs = booksSchema;
    const mockSchema = makeExecutableSchema({ typeDefs });

    addMockFunctionsToSchema({
        schema: mockSchema,
        mocks: {
            Boolean: () => false,
            ID: () => '1',
            Int: () => 1,
            Float: () => 1.1,
            String: () => 'Title',
        }
    });

    test('Has valid type definitions', async () => {
        expect(async () => {
            const MockServer = mockServer(typeDefs);

            await MockServer.query(`{ __schema { types { name } } }`);
        }).not.toThrow();
    });

    cases.forEach(obj => {
        const { id, query, variables, context: ctx, expected } = obj;

        test(`Testing Query: ${id}`, async () => {
            return await expect(
                graphql(mockSchema, query, null, { ctx }, variables)
            ).resolves.toEqual(expected);
        });
    });

});

GraphQL Schema and Resolver Test

Extending the previous test as suggested by the article Effective Testing a GraphQL Server, this test affirms that GraphQL schema and resolvers are working correctly [packages/server-books/tests/Books.test.js].

import { makeExecutableSchema } from 'graphql-tools'
import { graphql } from 'graphql'
import resolvers from '../src/resolvers'
import typeDefs from '../src/schema'

const titleTestCase = {
    id: 'Query Title',
    query: `
      query {
        books {
            title
        }
      }
    `,
    variables: {},
    context: {},
    expected: { data: { books: [{ title: 'Harry Potter and the Chamber of Secrets' }, { title: 'Jurassic Park' }] } }
};

describe('Test Cases', () => {

    const cases = [titleTestCase]
    const schema = makeExecutableSchema({ typeDefs: typeDefs, resolvers: { Query: resolvers } })

    cases.forEach(obj => {
        const { id, query, variables, context, expected } = obj

        test(`query: ${id}`, async () => {
            const result = await graphql(schema, query, null, context, variables)
            return expect(result).toEqual(expected)
        })
    })
})

Conclusion

As with the previous two articles on getting started with Apollo etc. the code developed again aims to be as minimalistic as possible. It shows how Apollo client/server code may be tested in three different ways. These are quite exhaustive, even if the presented tests are simplistic.

The only test missing is an integration tests which will test the React component linked to a live Apollo server back-end. I am not sure if it is possible to run an ’embedded’ Apollo server in the browser. Running such a server for testing the React component would also be a good addition.

GraphQL, Node.JS and React Monorepo Starter Kit

Following the GraphQL Apollo Starter Kit (Lerna, Node.js), I wanted to dig deeper into developing a monorepo for a GraphQL/React client-server application.

Unfortunately, things are not as easy as I thought at first. Chiefly the create-react-app template does not appear to work very well with monorepos and local dependencies to other packages.

That’s why I put together a small, simple starter template for developing modular client-server applications using React, GraphQL and Node.js. Here is the code on GitHub:

nodejs-react-monorepo-starter-kit

Some things to note:

  • There are four packages in the project
    • client-main: The React client, based on create-react-app
    • client-components: Contains a definition of the component app. Used by client-main
    • server-main: The Node.js server definition
    • server-books: Contains schema and resolver for GraphQL backend. Used by server-main.
  • Each package defines it’s own package.json and can be built independent of the other packages.
  • The main entry point for the dependent packages (client-components and server-books) is set to dist/index.js. This way, packages which use them, can use the transpiled version created by babel and don’t need to worry about specific JS features used in the dependent packages.

Like GraphQL Apollo Starter Kit (Lerna, Node.js) this starter kit is meant to be very basic to allow easy exploration of the source code.

GraphQL Apollo Starter Kit (Lerna, Node.js)

In many ways developing in Node.js is very fast and lightweight. However it can also be bewildering at times. Mostly so since for everything there seems to be more than one established way of doing things. Moreover, the right way to do something can change within 3 to 6 months, so best practices documented in books and blogs quickly become obsolete.

Some days ago I wanted to create a simple sample project that shows how to develop a simple client/server application using Apollo and React. I thought this would be a simple undertaking. I imagined I would begin with a simple tutorial or ‘starter kit’ and quickly be up and running.

I found that things were not as easy as I imagined, since there are plenty of examples to spin up a simple react app chiefly using create-react-app. I also found the awesome apollo-universal-starter-kit. However, the former lacks insight of how to link this to a Node.js back-end server and the latter is a bit complex and opinionated in some ways as to which frameworks to use.

This motivated me to develop a small, simple ‘starter kit’ for Apollo Client and Server in GraphQL with the following features:

  • Uses ES 2018 ‘vanilla’ JavaScript
  • Uses Lerna to define project with two packages (client and server)
  • Uses Node.js / Express as web server
  • Uses Babel to allow using ES 6 style modules for Node.js
  • Provides easy ways to start a development server and spin up a production instance

Here a link to the project on GitHub:

graphql-apollo-starter-kit

The README provides the instructions to run and build the project.

A few things of note about the implementation:

This project is aimed at developers new to Node.js/React/Apollo. It is not implemented in the most elegant way possible but in a way which makes it easy to understand what is going on by browsing through the code. Be welcome to check out the project and modify it!