Testcontainers Demo

This demo is part of a presentation at the Salzburg Web Dev Meetup June 2023. Slides are available here.

Prerequisites

Docker must be installed and executable without requiring interaction (e.g. sudo password). Docker Desktop should work out of the box. On Linux, it's usually necessary to add your user to the docker group and starting a fresh desktop session for the group change to take effect. This should even work with Docker for Windows.

Setup

1. npm install
2. docker-compose up

By default, the API is available at 0.0.0.0:8080.

API

This demo consists of a simple API that is backed by Redis. These operations are available:

• GET /:term - returns the count for this particular term.
• POST /:term - increments this term's counter by 1.
• DELETE /:term - resets the count and forgets the term.
• GET / - lists all terms that have been incremented before along with their count.
• DELETE / - resets all counts and forgets all terms.

Tests

This is the interesting part. Check the sources and run them using npm test.

To see the benefits of Testcontainers, compare test/api.{mock,real}.spec.js: Both feature the same test cases, one of them using mocks, one of them with real Redis.

Spoiler alert: Although the tests using mocks aren't that much verbose (~20% longer), their coverage is much less thorough. Additionally, using mocks requires piercing through abstraction layers, whereas the Testcontainers version stays consistently on the API level.