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Custom Jest Assertions for Serverless Projects

sls-test-tools provides a range of utilities, setup, teardown and assertions to make it easier to write effective and high quality integration tests for Serverless Architectures on AWS.

🚧 This is in an alpha state while we trial a few initial assertions and get feedback on the approach and structure. 🚧

⚠️ AWS resources will be created (SQS Queue, EventBridge Rule...) if the EventBridge module is used. Although there is clear setup and teardown we do not advise running this on production environments currently. ⚠️


With npm:

npm install --save-dev sls-test-tools

With yarn:

yarn add -D sls-test-tools


sls-test-tools is currently being actively maintained, yet is in alpha. Your feedback is very welcome.






    await expect("BUCKET NAME").toHaveS3ObjectWithNameEqualTo("FILE NAME");
    // note this is an async assertion and requires "await"



AWSClient - An AWS client with credentials set up

getStackResources(stackName) - get information about a stack
getOptions() - get options for making requests to AWS


An interface to the deployed EventBridge, allowing events to be injected and intercepted via an SQS queue and EventBridge rule.

Static - create a EventBridge instance to allow events to be injected and intercepted


    eventBridge.publishEvent(source, detailType, detail) - publish an event to the bus
    eventBridge.getEvents() - get the events that have been sent to the bus
    eventBridge.clear() - clear old messages
    eventBridge.destroy() - remove infastructure used to track events

Running with jest


  • When running tests with jest using sls-test-tools matchers there are certain parameters needed for sls-test-tools to make assertions.
  • These are passed as command line arguments, using quotation to match jests convention on test arguments.


  • '--stack=my-service-dev' - the CloudFormation stack name of the stack under test.


  • '--profile=[PROFILE NAME]' (will default to default)

  • '--region=[AWS Region]' (will default to eu-west-2)

  • '--keep=true' - keeps testing resources up to avoid creation throttles (e.g. SQS Queue created for EventBridge assertions)

  • To avoid issues we recommend --runInBand

import { AWSClient, EventBridge } from "sls-test-tools";

const lambda = new AWSClient.Lambda()
let eventBridge;
const s3 = new AWSClient.S3()

describe("Integration Testing Event Bridge", () => {
  beforeAll(async () => {
    eventBridge = await"event-bridge")

  afterAll(async () => {
    await eventBridge.destroy()

  it("correctly publishes an event to the event bus when the lambda is invoked", async () => {
    const event = {
      body: JSON.stringify({
        filename: filename,

    // Invoke Lambda Function
    const params = {
      FunctionName: "event-bridge-example-dev-service1",
      Payload: JSON.stringify(event),
    await lambda.invoke(params).promise();

    const eventBridgeEvents = await eventBridge.getEvents()

  it("correctly generates a PDF when an order is created", async () => {
    await eventBridge
      .publishEvent("order.created", "example", JSON.stringify({ filename: filename }));

    await sleep(5000); // wait 5 seconds to allow event to pass

    const params = {
      Bucket: "example-dev-thumbnails-bucket",
      Key: filename,

    // Assert that file was added to the S3 bucket
    const obj = await s3.getObject(params).promise();


Thanks goes to these wonderful people (emoji key):

Ben Ellerby

💻 🖋 📖 🤔 🎨 📢 👀

Sarah Hamilton

💻 🖋 📖 🤔

Alex White


This project follows the all-contributors specification. Contributions of any kind welcome!