Dockest
Dockest is an integration testing tool aimed at alleviating the process of evaluating unit tests whilst running multi-container Docker applications.
Table of contents
Introduction
Motivation
The original motivation for Dockest, along with real world examples, can be read in this blog article.
Dockest was born out of frustration and with a vision to make developers’ lives slightly less miserable.
Dockest provides an abstraction for your Docker services’ lifecycles during integration testing, freeing developers from convoluted and flaky shell scripts. Adopting Dockest is super easy regardless if you’ve got existing tests or not and doesn’t necessarily require additional CI pipeline steps.
Why Dockest
The value that Dockest provides over e.g. plain docker-compose is that it figures out the connectivity and responsiveness status of each individual service (either synchronously or asynchronously) and once all services are ready the tests run.
Example use cases
Dockest can be used in a variety of use cases and situations, some of which can be found under
packages/examples
.
AWS CodeBuild
What is AWS CodeBuild?
Cool, can I run it locally?
You can now locally test and debug your AWS CodeBuild builds using the new CodeBuild local agent.
Node.js to Node.js
Dockest can also build and run application services as part of your integration tests.
Basic Usage
System requirements
In order to run Dockest, there's a few system requirements:
- Dockest uses Jest's programmatic CLI and requires Jest v20.0.0 or newer to work
- Docker
- Docker Compose ("On desktop systems like Docker Desktop for Mac and Windows, Docker Compose is included as part of those desktop installs.")
Install
yarn add --dev dockest
# npm install --save-dev dockest
Application code
// cache.ts
export const cacheKey = 'arbitraryNumberKey';
export const setCache = (redisClient: Redis, arbitraryNumber: number) => {
redisClient.set(cacheKey, arbitraryNumber);
};
Unit tests
// cache.spec.ts
import Redis from 'ioredis'; // ... or client of choice
import { cacheKey, setCache } from './cache';
const redisClient = new Redis({
host: 'localhost',
port: 6379, // Match with configuration in docker-compose.yml
});
it('should cache an arbitrary number', async () => {
const arbitraryNumber = 5;
await setCache(redisClient, arbitraryNumber);
const cachedValue = await redisClient.get(cacheKey);
expect(cachedValue).toEqual(arbitraryNumber);
});
Dockest integration tests
Transform unit test into an integration test by creating a docker-compose.yml
and dockest.ts
file.
Important note for the Compose file
Dockest expects services' ports to be defined using long format and works best with high versions of docker-compose (i.e. 3.7 or higher)
# docker-compose.yml
version: '3.8'
services:
myRedis:
image: redis:5.0.3-alpine
ports:
- published: 6379
target: 6379
// dockest.ts
import { Dockest } from 'dockest';
const dockest = new Dockest();
// Specify the services from the Compose file that should be included in the integration test
const dockestServices = [
{
serviceName: 'myRedis', // Must match a service in the Compose file
},
];
dockest.run(dockestServices);
Configure scripts
Configure package.json
to run dockest.ts
. ts-node
is recommended for
TypeScript projects.
{
"scripts": {
"test": "ts-node ./dockest"
},
"devDependencies": {
"dockest": "...",
"ts-node": "..."
}
}
Run
Finally, run the tests:
yarn test
Development
Publishing a new version
Prep
- Decide on a version. Let's reference it as
<VERSION>
- e.g.
v1.0.0
, append-alpha.0
or-beta.0
to inform the CI to publish the package to npm as such (i.e. not as "latest")
- e.g.
- Create release branch
git checkout -b "release-v<VERSION>"
- Make sure
CHANGELOG.md
contains the changes for the upcoming version
Creating a new version
- Be in release branch
- Make sure all changes are pushed to remote
- Run
yarn lerna version <VERSION>
(e.g.yarn lerna version v3.0.0-beta.0
) from project root, this will:- Bump all packages configured with Lerna
- Create a git tag
- Push changes and tags (
git push --tags
to include tags)
From here, the pipeline will publish the library's new version to npm
Clean up
- Merge release branch into master
- Delete release branch
Contributing
Setup and testing
This is a monorepo using lerna, meaning all scripts can be run from root.
yarn prep
will executes the necessary scripts to install dependencies for all packages (including root) as well as
build whatever needs building.
yarn dev:link
will link the library source to each example, making developing a smoother experience.
API Reference
DockestOpts
import { Dockest } from 'dockest';
const { run } = new Dockest(opts);
DockestOpts
DockestOpts
is optional, i.e. the dockest constructor can be called without arguments.
DockestOpts
structure:
property | type | default |
---|---|---|
composeFile | string |
docker-compose.yml |
composeOpts | object |
see paragraph on composeOpts |
debug | boolean |
false |
dumpErrors | boolean |
false |
exitHandler | function |
null |
jestLib | object |
require('jest') |
jestOpts | object |
{} |
logLevel | object |
logLevel.INFO , i.e. 3
|
runInBand | boolean |
true |
DockestOpts.composeFile
Compose file(s) with services to use while running tests
DockestOpts.composeOpts
composeOpts
structure:
property | desription | type | default |
---|---|---|---|
alwaysRecreateDeps | Recreate dependent containers. Incompatible with --no-recreate
|
boolean |
false |
build | Build images before starting containers | boolean |
false |
forceRecreate | Recreate containers even if their configuration and image haven't changed | boolean |
false |
noBuild | Don't build an image, even if it's missing | boolean |
false |
noColor | Produce monochrome output | boolean |
false |
noDeps | Don't start linked services | boolean |
false |
noRecreate | If containers already exist, don't recreate them. Incompatible with --force-recreate and -V
|
boolean |
false |
quietPull | Pull without printing progress information | boolean |
false |
Forwards options to docker-compose up
, Docker's docs.
DockestOpts.debug
Pauses Dockest just before executing Jest. Useful for more rapid development using Jest manually
DockestOpts.dumpErrors
Serializes errors and dumps them in dockest-error.json
. Useful for debugging.
DockestOpts.exitHandler
Callback that will run before exit. Received one argument of type { type: string, code?: number, signal?: any, error?: Error, reason?: any, p?: any }
DockestOpts.jestLib
The Jest library itself, typically passed as { lib: require('jest') }
. If omitted, Dockest will attempt to require
Jest from your application's dependencies. If absent, Dockest will use it's own version.
DockestOpts.jestOpts
Jest's CLI options, an exhaustive list of CLI-options can be found in Jest's documentation
DockestOpts.logLevel
Decides how much logging will occur. Each level represents a number ranging from 0-4
DockestOpts.runInBand
[boolean]
Initializes and runs the Runners in sequence. Disabling this could increase performance
Note: Jest runs tests in parallel per default, which is why Dockest defaults runInBand
to true
. This will cause
jest to run sequentially in order to avoid race conditions for I/O operations. This may lead to longer runtimes.
Run
import { Dockest } from 'dockest';
const { run } = new Dockest();
const dockestServices = [
{
serviceName: 'service1',
commands: ['echo "Hello name1 🌊"'],
dependents: [
{
serviceName: 'service2',
},
],
readinessCheck: () => Promise.resolve(),
},
];
run(dockestServices);
DockestService
Dockest services are meant to map to services declared in the Compose file(s)
DockestService
structure:
property | type | default |
---|---|---|
name | string |
property is required |
commands | (string | function)[] => string[] |
[] |
dependents | DockestService[] |
[] |
readinessCheck | function |
() => Promise.resolve() |
DockestService.name
Service name that matches the corresponding service in your Compose file
DockestService.commands
Bash scripts that will run once the service is ready. E.g. database migrations.
Can either be a string, or a function that generates a string. The function is fed the container id of the service.
DockestService.dependents
dependents
are Dockest services that are are dependent on the parent service.
For example, the following code
const dockestServices = [
{
serviceName: 'service1',
dependents: [
{
serviceName: 'service2',
},
],
},
];
will ensure that service1
starts up and is fully responsive before even attempting to start service2
.
Why not rely on the Docker File service configuration options
depends_on
?
Docker's docs explains this very neatly:
version: '3.8'
services:
web:
build: .
depends_on:
- db
- redis
redis:
image: redis
db:
image: postgres
depends_on
does not wait fordb
andredis
to be “ready” before startingweb
- only until they have been started.
DockestService.readinessCheck
The Dockest Service's readinessCheck function helps determining a service's readiness (or "responsiveness") by, for
example, querying a database using select 1
. The readinessCheck function receive the corresponding Compose service
configuration from the Compose file as first argument and the containerId as the second.
The readinessCheck takes a single argument in form of an object.
const dockestServices = [
{
serviceName: 'service1',
readinessCheck: async ({
containerId,
defaultReadinessChecks: { postgres, redis, web },
dockerComposeFileService: { ports },
logger,
}) => {
// implement your readinessCheck...
},
},
];
readinessCheck
structure:
property | description |
---|---|
containerId | The Docker container's id. |
defaultReadinessChecks | Dockest exposes a few default readinessChecks that developers can use. These are plug-and-play async functions that will attempt to establish responsiveness towards a service. |
dockerComposeFileService | This is an object representation of your service's information from the Compose file. |
logger | An instance, specific to this particular Dockest Service (internally known as Runner), of the internal Dockest logger. Using this logger will prettify and contextualize logs with e.g. the serviceName. |
defaultReadinessChecks
defaultReadinessChecks.postgres
The default readiness check for PostgreSQL is based on this image which expects certain environment variables.
# docker-compose.yml
version: '3.8'
services:
postgres: # (1)
image: postgres:9.6-alpine
ports:
- published: 5432
target: 5432
environment: # (2)
POSTGRES_DB: baby
POSTGRES_USER: dont
POSTGRES_PASSWORD: hurtme
// dockest.ts
import { Dockest } from 'dockest';
const { run } = new Dockest();
run([
{
serviceName: 'postgres', // must match (1)
readinessCheck: async ({
defaultReadinessChecks: { postgres },
dockerComposeFileService: {
environment: { POSTGRES_DB, POSTGRES_USER }, // must match (2)
},
}) => postgres({ POSTGRES_DB, POSTGRES_USER }),
},
]);
defaultReadinessChecks.redis
The default readiness check for Redis is based on this image which is plug-and-play.
# docker-compose.yml
version: '3.8'
services:
redis: # (1)
image: redis:5.0.3-alpine
ports:
- published: 6379
target: 6379
// dockest.ts
import { Dockest } from 'dockest';
const { run } = new Dockest();
run([
{
serviceName: 'redis', // must match (1)
readinessCheck: ({ defaultReadinessChecks: { redis } }) => redis(),
},
]);
defaultReadinessChecks.web
[WIP]
Requires wget. The image would most likely be a self-built web service.
The exact use case should be fleshed out.
// dockest.ts
import { Dockest } from 'dockest';
const { run } = new Dockest();
run([
{
serviceName: 'web', // must match (1)
readinessCheck: async ({ defaultReadinessChecks: { web } }) => web(),
},
]);
Utils
logLevel
object
Helper constant for DockestOpts
import { logLevel } from 'dockest';
console.log(logLevel);
// {
// NOTHING: 0,
// ERROR: 1,
// WARN: 2,
// INFO: 3,
// DEBUG: 4
// }
sleep
function
Sleeps for X milliseconds.
import { sleep } from 'dockest';
const program = async () => {
await sleep(1337);
};
program();
sleepWithLog
function
Sleeps for X seconds, printing a message each second with the progress.
import { sleepWithLog } from 'dockest';
const program = async () => {
await sleepWithLog(13, 'sleeping is cool');
};
program();
execa
function
Exposes the internal wrapper of the execa
library.
import { execa } from 'dockest';
const opts = {
logPrefix,
logStdout,
execaOpts,
runner,
};
const program = async () => {
await execa(`echo "hello :wave:"`, opts);
};
program();
opts
structure:
property | description | type | default |
---|---|---|---|
logPrefix | Prefixes logs | string |
'[Shell]' |
logStdout | Prints stdout from the child process |
boolean |
false |
execaOpts | Options passed to the execa function | object |
{} |
runner | Internal representation of a DockestService. Ignore this | Runner |
- |
Versioned Documentation
Acknowledgements
Thanks to Juan Lulkin for the logo ❤️
Thanks to Laurin Quast for great ideas and contributions 💙
License
MIT