@shelf/jest-dynamodb

Run your tests using Jest & DynamoDB local

Usage no npm install needed!

<script type="module">
  import shelfJestDynamodb from 'https://cdn.skypack.dev/@shelf/jest-dynamodb';
</script>

README

jest-dynamodb CircleCI npm (scoped)

Jest preset to run DynamoDB Local

Usage

0. Install

$ yarn add @shelf/jest-dynamodb --dev

Make sure aws-sdk is installed as a peer dependency. And java runtime available for running DynamoDBLocal.jar

1. Create jest.config.js

module.exports = {
  preset: '@shelf/jest-dynamodb'
};

2. Create jest-dynamodb-config.js

2.1 Properties

tables
  • Type: object[]
  • Required: true

Array of createTable params.

port
  • Type: number
  • Required: false

Port number. The default port number is 8000.

options
  • Type: string[]
  • Required: false

Addtional arguments for dynamodb-local. The default value is ['-sharedDb'].

clientConfig
  • Type: object
  • Required: false

Constructor params of DynamoDB client.

installerConfig
  • Type: {installPath?: string, downloadUrl?: string}

  • Required: false

  • installPath defines the location where dynamodb-local is installed or will be installed.

  • downloadUrl defines the url of dynamodb-local package.

The default value is defined at https://github.com/rynop/dynamodb-local/blob/2e6c1cb2edde4de0dc51a71c193c510b939d4352/index.js#L16-L19

2.2 Examples

You can set up tables as an object:

module.exports = {
  tables: [
    {
      TableName: `files`,
      KeySchema: [{AttributeName: 'id', KeyType: 'HASH'}],
      AttributeDefinitions: [{AttributeName: 'id', AttributeType: 'S'}],
      ProvisionedThroughput: {ReadCapacityUnits: 1, WriteCapacityUnits: 1}
    }
    // etc
  ],
  port: 8000
};

Or as an async function (particularly useful when resolving DynamoDB setup dynamically from serverless.yml):

module.exports = async () => {
  const serverless = new (require('serverless'))();
  // If using monorepo where DynamoDB serverless.yml is in another directory
  // const serverless = new (require('serverless'))({ servicePath: '../../../core/data' });

  await serverless.init();
  const service = await serverless.variables.populateService();
  const resources = service.resources.filter(r => Object.keys(r).includes('Resources'))[0];

  const tables = Object.keys(resources)
    .map(name => resources[name])
    .filter(r => r.Type === 'AWS::DynamoDB::Table')
    .map(r => r.Properties);

  return {
    tables,
    port: 8000
  };
};

Or read table definitions from a CloudFormation template (example handles a !Sub on TableName, i.e. TableName: !Sub "${env}-users" ):

const yaml = require('js-yaml');
const fs = require('fs');
const {CLOUDFORMATION_SCHEMA} = require('cloudformation-js-yaml-schema');

module.exports = async () => {
  const cf = yaml.safeLoad(fs.readFileSync('../cf-templates/example-stack.yaml', 'utf8'), {
    schema: CLOUDFORMATION_SCHEMA
  });
  var tables = [];
  Object.keys(cf.Resources).forEach(item => {
    tables.push(cf.Resources[item]);
  });

  tables = tables
    .filter(r => r.Type === 'AWS::DynamoDB::Table')
    .map(r => {
      let table = r.Properties;
      if (typeof x.TableName === 'object') {
        table.TableName = table.TableName.data.replace('${env}', 'test');
      }
      delete table.TimeToLiveSpecification; //errors on dynamo-local
      return table;
    });

  return {
    tables,
    port: 8000
  };
};

3. 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);

4. PROFIT! 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'
  });
});

Troubleshooting

UnknownError: Not Found

Perhaps something is using your port specified in jest-dynamodb-config.js.

Alternatives

  • jest-dynalite - a much lighter version which spins up an instance for each runner & doesn't depend on Java

Read

Used by

See Also

Publish

$ git checkout master
$ yarn version
$ yarn publish
$ git push origin master --tags

License

MIT © Shelf