how-to-express-microservice
An opinionated, personal template for a testable express.js http service
Getting Started
Try it out with some http requests
# get message
curl http://localhost:9000/greeting
# update message
curl -XPUT -H 'Content-Type: application/json' -d '{"message": "hola, mundo"}' http://localhost:9000/greeting
Technologies
- yarn for package management
- express.js for http routing
- mocha, chai, sinon for test runners, assertions, and mocking
- supertest for http integration tests
Architecture
./index.js uses the factory method defined in ./app.js to construct an
express.js app object from a set of components. In this example, there is one
such component, ./components/greeting.
Each component directory defines an index.js which exports a configured
express Router: this is a
component's public API. Internally, the component likely defines a number of
testable modules for interacting with databases, external services, etc.
Each component's routes.js module defines the skinny controller layer that
translates http requests into messages for domain services then translates the
responses from those domain services to http responses. This routes.js module
is testable because it defines a factory method that allows the router to use
mock implementations of domain services.
supertest does a great job of making
assertions about the router's behavior as seen in
./components/greeting/routes.spec.js.
Component services communicate errors to the routing layer by ways of throwing
an Error or returning a rejected Promise which contains an Error. The
./errors/map-error.js module is responsible for translating domain errors to
HTTP responses.