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. ⚠️

Installation

With npm:

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

With yarn:

yarn add -D sls-test-tools

Maintenance

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

Assertions:

EventBridge

    expect(eventBridgeEvents).toHaveEvent();

    expect(eventBridgeEvents).toHaveEventWithSource("order.created");

S3

Note: these async assertions require "await"

    await expect("BUCKET NAME").toHaveS3ObjectWithNameEqualTo("FILE NAME");

    await expect("BUCKET NAME").toExistAsS3Bucket();

    await expect({
      bucketName: "BUCKET_NAME",
      objectName: "FILE NAME",
    }).toHaveContentTypeEqualTo("CONTENT_TYPE");;

where CONTENT_TYPE are standards MIME types

    await expect({
      bucketName: "BUCKET_NAME",
      objectName: "FILE NAME",
    }).toHaveContentEqualTo("CONTENT");

Step Functions

Note: these assertions also require "await"

    await expect("STATE_MACHINE_NAME").toHaveCompletedExecutionWithStatus("STATUS");
    await expect("STATE_MACHINE_NAME").toMatchStateMachineOutput({EXPECTED_OUTPUT}));

DynamoDB

Note: these assertions also require "await"

    await expect("TABLENAME").toContainItemWithValues({[field]: value});
    await expect({PK: pk,
                  SK: sk,
                }).toExistInDynamoTable('TABLENAME');

Cognito

Note: this assertion also requires "await"

  await expect('USER_POOL_ID').toContainUser('USERNAME');

Helpers

General

AWSClient - An AWS client with credentials set up

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

EventBridge

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

Static

    EventBridge.build(busName) - create a EventBridge instance to allow events to be injected and intercepted

Instance

    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

Step Functions

An interface to a deployed Step Function, with a function to execute a Step Function until its completion.

Static

  StepFunctions.build() // create a Step Functions Client for executing existing state machines

Instance

  stepFunctions.runExecution(stateMachineName, input) // executes state machine until completion

Running with jest

Arguments

• 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 either as command line arguments, using quotation to match jests convention on test arguments, or by using environment variables. CLI arguments override environment variables.

Required

• '--stack=my-service-dev' or process.env.CFN_STACK_NAME - the CloudFormation stack name of the stack under test.

Optional

• '--profile=[PROFILE NAME]' or process.env.AWS_PROFILE (will default to default)

• '--region=[AWS Region]' or process.env.AWS_REGION (will default to eu-west-2)

• '--keep=true' or process.env.SLS_TEST_TOOLS_KEEP (will default to false) - keeps testing resources up to avoid creation throttles (e.g. SQS Queue created for EventBridge assertions)

• '--event-rule-name=[Event Bus Rule Name]' - Custom Event bridge Rule name (will deafult to test-${eventBridgeName}-rule)

• '--queue-name=[SQS Queue Name]' - Custom SQS Queue name (will deafult to ${eventBridgeName}-testing-queue)

• 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 EventBridge.build("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()
    expect(eventBridgeEvents).toHaveEvent();
    expect(eventBridgeEvents).toHaveEventWithSource("order.created");
  });

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

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

    const params = {
      Bucket: bucketName,
      Key: filename,
    };

    // Assert that file was added to the S3 bucket
    await expect("example-dev-thumbnails-bucket").toHaveS3ObjectWithNameEqualTo(
      filename
    );
  });

Contributors ✨

Thanks goes to these wonderful people (emoji key):

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