Docker container for app tests with postgres database - postgresql

Question

I'm new to Docker.
I'm trying to run my node app tests in a Docker container.
I want to run the tests with a real postgres db.
I'm creating this container with the following Dockerfile:
# Set image
FROM postgres:alpine
# Install node latest
RUN apk add --update nodejs nodejs-npm
# Set working dir
WORKDIR .
# Copy the current directory contents into the container at .
ADD src src
ADD .env.testing .env
ADD package.json .
ADD package-lock.json .
# Run tests
CMD npm install && npm run coverage
From the image docs, when I run the container with:
$ docker run build-name -d postgres
I see that the container takes time to start postgresql service.
When I run the container without the "-d postgres" param:
$ docker run build-name
The service does not start and the tests fail due to "could not connect to server".
Questions:
A. How can I run the tests AFTER the postgresql service starts?
B. I saw some examples using docker-composer but can I do this without composer?
Thanks

Answer 1

Thanks to #Bogdan I found the complete solution:
Dockerfile should be:
# Set image
FROM postgres:alpine
# Install node latest
RUN apk add --update nodejs nodejs-npm
# Set working dir
WORKDIR .
# Copy the current directory contents into the container at .
ADD src src
ADD .env.testing .env
ADD package.json .
ADD package-lock.json .
# Install
RUN npm install
# Init container
CMD psql -U postgres -c "SELECT 1;" postgres
Build container:
$ docker build -t test .
Run container:
$ docker run --name startedtest -d test -d postgres
Run tests after conatiner is running:
$ docker exec startedtest some_create_schema_script && npm run coverage

Answer 2

If the goal is just to run the tests in the Postgres container, one solution could be to install NodeJs in your postgres:alpine derived image and run the container normally. Once the database is up, you can run npm using docker exec like this:
docker exec <container_id> npm run coverage