Using Jest with DynamoDB: Configuration and Testing Guide

By using the Global Setup/Teardown and Async Test Environment APIs, Jest will work smoothly with DynamoDB.

Use jest-dynamodb Preset

Jest DynamoDB will provide all required configuration to run your tests using DynamoDB.

We will walk you through the steps required to run a Jest test on a DynamoDB

1. First you need to install @shelf/jest-dynamodb

yarn add @shelf/jest-dynamodb -dev

2. Then you should specify preset in your Jest configuration:

{
  "preset": "@shelf/jest-dynamodb"
}

3. Next thing you need to do is to create jest-dynamodb-config.js and define the DynamoDB tables

module.exports = {
  tables: [
    {
      TableName: `files`,
      KeySchema: [{AttributeName: 'id', KeyType: 'HASH'}],
      AttributeDefinitions: [{AttributeName: 'id', AttributeType: 'S'}],
      ProvisionedThroughput: {ReadCapacityUnits: 1, WriteCapacityUnits: 1},
    },
    // etc
  ],
};

4. After that, you should configure DynamoDB client

const {DocumentClient} = require('aws-sdk/clients/dynamodb');

const isTest = process.env.JEST_WORKER_ID;
const config = {
  convertEmptyValues: true,
  ...(isTest && {
    endpoint: 'localhost:8000',
    sslEnabled: false,
    region: 'local-env',
  }),
};

const ddb = new DocumentClient(config);

5. Finally, you can then write tests

it('should insert item into table', async () => {
  await ddb
    .put({TableName: 'files', Item: {id: '1', hello: 'world'}})
    .promise();

  const {Item} = await ddb.get({TableName: 'files', Key: {id: '1'}}).promise();

  expect(Item).toEqual({
    id: '1',
    hello: 'world',
  });
});

Let us run an example that encompasses both the configuration and the test itself:

//require dynamodb library
const {DocumentClient} = require('aws-sdk/clients/dynamodb');

const isTest = process.env.JEST_WORKER_ID;
//set your configurations
const config = {
  convertEmptyValues: true,
  ...(isTest && {
    endpoint: 'localhost:8000',
    sslEnabled: false,
    region: 'local-env',
  }),
};
//creates an instance of the config set above
const ddb = new DocumentClient(config);
//now write a mock
it('should insert item into table', async () => {
  await ddb
    .put({TableName: 'files', Item: {id: '1', hello: 'world'}})
    .promise();

  const {Item} = await ddb.get({TableName: 'files', Key: {id: '1'}}).promise();

  expect(Item).toEqual({
    id: '1',
    hello: 'world',
  });
});

Just like in the test using MongoDB there is no need to load any dependencies.

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Next: Configuring Jest with MongoDB: A Step-by-Step Guide.