lambda-tester

lambda-tester

Simplifies writing unit tests for AWS Lambda functions using Node.js.

Features

• Verifies correct handler behavior
• Mocks event types with code
• Works asynchronously
• Supports Promises
• Verifies Node.js runtime version
• AWS X-Ray support [experimental]
• Detects resource leaks [experimental]
• Easily integrates with test frameworks (Mocha and Jasmine)
• Handlers can be loaded and removed after execution
• Lightweight and won't impact performance
• Maps the environment variable LAMBDA_TASK_ROOT to the application's root
• Automatically loads .env files
• Works with Node 10.x, and 12.x

Installation

Install via npm.

npm install lambda-tester --save-dev

Getting Started

Lambda handlers with support for callbacks use the typical Node.js asynchronous signature:

exports.handler = function( event, context, callback ) {

    callback( null, 'success!' );
}

The following example shows a simple case for validating that the Lambda (handler) was called successfully (i.e. callback( null, result ):

const LambdaTester = require( 'lambda-tester' );

const myHandler = require( '../index' ).handler;

describe( 'handler', function() {

	it( 'test success', async function() {

		await LambdaTester( myHandler )
			.event( { name: 'Fred' } )
			.expectResult();
	});
});

If the handler calls callback( err ), then the test will fail.

Additionally, if one wanted to test for failure, then the following code would be used:

const LambdaTester = require( 'lambda-tester' );

const myHandler = require( '../index' ).handler;

describe( 'handler', function() {

	it( 'test failure', async function() {

		await LambdaTester( myHandler )
			.event( { name: 'Unknown' } )
			.expectError();
	});
});

Note: you must either return the LambdaTester instance back to the testing framework or use the await/async keywords.

Documentation

Complete documentation can be found in our documentation page.

Projects Using lambda-tester

• vandium - Secures and simplifies AWS Lambda handlers

Feedback

We'd love to get feedback on how you're using lambda-tester and things we could add to make this tool better. Feel free to contact us at [e-mail]

Compatibility

Starting with version 4.0, lambda-tester supports node versions 10 and higher. If you require support for older versions of node, then use a previous version of lambda-tester.

License

BSD-3-Clause

Changelog

4.0.0 (2019-11-23)

Breaking:

• Strict checking for how the results/errors are captured have been relaxed. this can be re-enabled using the strict() method after creating the LambdaTester instance.

• Node.js versions are no longer checked before running the tests.

New:

• Event mocks (via lambda-event-mock)

Updated:

• expectResult() and expectError() are now the preferred methods to verify the handler's execution. If strict mode is enabled, then it will enforce that the callback is called.
• Better support for stack traces. Thanks @edbo @d-w4lsh
• Supports nodejs 12. Thanks @jkehres

Internal:

• Updated dependencies
• Refactored unit tests