Separate docker-compose file for testing NestJS - docker

Question

I have got main docker-compose file like that:
services:
main:
container_name: main
build:
dockerfile: Dockerfile
context: './backend/'
ports:
- '${APP_PORT}:3000'
volumes:
- './backend/src:/backend/src'
depends_on:
- mongo
mongo:
container_name: mongodb
image: mongo
ports:
- '27017:27017'
environment:
...
volumes:
- mongo-data:/data/db
volumes:
mongo-data:
/backend/Dockerfile (root NestJS folder):
FROM node:14
WORKDIR /backend
COPY package*.json ./
RUN npm install
COPY src/ tsconfig*.json ./
CMD ["npm", "run", "start:dev"]
As you can see, there is only src folder in my container, which is good and intended. However, I would like to create a separate container only for testing my application, so instead of just the "src" folder I have to include the "tests" folder as well (or only tests folder and use src folder of this container?). Apart from that, I would also like to run the "jest" command to run unit tests contained in folders in the src folder.
I have no idea how to do this. Can I share folders through multiple containers or something like that?

Answer 1

One way would be to change you Dockerfile to a multi-stage build with a testing stage.
Here I have added a prod and a testing stage as well as your original (dev) build stage.
FROM node:14 as dev
WORKDIR /backend
COPY package*.json ./
RUN npm install
COPY src/ tsconfig*.json ./
CMD ["npm", "run", "start:dev"]
FROM dev as testing
COPY tests ./
ENV CI=true
RUN ["npn", "run", "test"]
FROM dev as prod
LABEL version="1.0" "com.example.image"="My Image"
CMD ["npm", "run", "start"]
The you can specify the build target you want with a variable in your docker-compose-file.
services:
main:
container_name: main
build:
dockerfile: Dockerfile
context: './backend/'
target: ${TARGET:-prod}
ports:
...
TARGET can be set in an .env file or by environment variable. I've set a default value so target becomes prod if not specified.
Other possible solutions would be to have multiple Dockerfiles or use a docker-compose.override.yml file with testing commands specified and different build context included.