lambda-tdd

Test Framework for AWS Lambda

Testing Framework for AWS Lambda. Very useful for integration testing as you can examine how your lambda function executes for certain input and specific environment variables. Tries to model the cloud execution as closely as possible.

What it does

• Tests are defined as JSON files
• Test are dynamically evaluated using Chai
• Lambda functions are executed using Lambda-Wrapper
• Supports external request mocking using Nock
• Allows setting of environment variables on a per test granularity
• Freeze execution to specific timestamp with Timekeeper
• Set lambda timeout (context.getRemainingTimeInMillis())
• Set test timeout
• Specify event input
• Test success and error responses

Example Projects

Example project using js-gardener and lambda-tdd can be found here.

Getting Started

To install run

$ npm install --save-dev lambda-tdd

Initialize Test Runner and Execute

const lambdaTester = require("lambda-tdd")({
  cwd: __dirname,
  verbose: process.argv.slice(2).indexOf("--debug") !== -1
});

describe("Testing Tester", () => {
  lambdaTester.execute((process.argv.slice(2)
    .find(e => e.startsWith("--filter=")) || "")
    .substring(9));
});

You can pass an array of test files to the execute() function or a regular expression pattern. By default tests are auto detected. If a pattern is passed in only matching tests are executed.

The example above allows for use of a --filter=REGEX parameter to only execute specific tests.

Test File Example

{
  "handler": "geoIp",
  "env": {
    "GOOGLE_PROJECT_ID": "123456789"
  },
  "event": {
    "ip": "173.244.44.10"
  },
  "nock": [{
    "to": {
      "match": "^.*?\"http://ip-api\\.(com|ca):80\".*?$"
    }
  }],
  "body": [{
    "to.contain": "\"United States\""
  }],
  "timestamp": 1511072994,
  "success": true,
  "lambdaTimeout": 5000,
  "timeout": 5000
}

More examples can be found here.

Test Runner Options

cwd

Type: string
Default: process.cwd()

Directory which other defaults are relative to.

name

Type string
Default: lambda-test

Name of this test runner for debug purposes.

verbose

Type boolean
Default: false

Display console output while running tests. Useful for debugging.

handlerFile

Type: string
Default: handler.js

Handler file containing the handler functions (specified in test).

cassetteFolder

Type: string
Default: __cassettes

Folder containing nock recordings.

envVarYml

Type: string
Default: env.yml

Specify yaml file containing environment variables. No existing environment variables can be overwritten.

testFolder

Type: string
Default: ``

Folder containing test files.

Test File Format

handler

Type: string
Required

The handler inside the handler file, i.e. if handler.js contained

module.exports.returnEvent = (event, context, cb) => cb(null, event);

we would set this to returnEvent.

env

Type object
Default: {}

Contains environment variables that are set for this test. Existing environment variables can be overwritten.

timestamp

Type unix
Default: Unfrozen

Set unix timestamp that test executing will see. Time does not progress if this option is set.

timeout

Type integer
Default: Mocha Default Timeout

Set custom timeout in ms for lambda execution. Handy e.g. when recording nock requests.

event

Type object
Default: undefined

Event object that is passed to lambda handler.

lambdaTimeout

Type integer
Default: 300000

Set initial lambda timeout in ms. Exposed in lambda function through context.getRemainingTimeInMillis(). The timeout is not enforced, but progresses as expected unless timestamp option is used.

success

Type boolean
Required

True iff execution is expected to succeed, i.e. no error is passed into callback.

response

Type array
Default: []

Dynamic expect logic executed against the response string. More details on dynamic expect handling below.

error

Type array
Default: []

Dynamic expect logic executed against the error string. More details on dynamic expect handling below.

body

Type array
Default: []

Dynamic expect logic executed against the response.body string. More details on dynamic expect handling below.

logs

Type array
Default: []

Dynamic expect logic executed against the console.log/info and console.error/warn output array. You can use errorLogs and defaultLogs to access them independently. More details on dynamic expect handling below.

defaultLogs

Type array
Default: []

See logs.

errorLogs

Type array
Default: []

See logs.

nock

Type array
Default: []

Dynamic expect logic executed against the nock recording. More details on dynamic expect handling below. Note that the nock recording must already exist for this check to evaluate correctly.

Important: If you are running into issues with replaying a cassette file you recorded previously, try editing the cassette and stripping information that might change. Also make sure cassette files never expose secret tokens or passwords!

Dynamic Expect Logic

Uses Chai Assertion Library syntax written as json. Lets assume we have an output array [1, 2] we want to validate. We can write

expect([1, 2]).to.contain(1);
expect([1, 2]).to.contain(2);

as the following json

[{
  "to.contain": 1
}, {
  "to": {
    "contain": 2
  }
}]

Note that targets are either arrays or strings, but never objects (design limitation).

Limitations

• Does currently not play nicely with native modules. This is because native modules can not be invalidated.

Contribution / What's next

Currently nothing planned