Gitlab CI how to run tests before building docker image - docker

Question

I have a Python based repository and I am trying to setup Gitlab CI to Build a Docker image using Dockerfile and pushing the image to Gitlab's Registry.
Before building and deploying the Docker image to registry, I want to run my unit tests using Python. Here is my current gitlab-ci.yml file that only does testing:
image: python:3.7-slim
before_script:
- pip3 install -r requirements.txt
test:
variables:
DJANGO_SECRET_KEY: some-key-here
script:
- python manage.py test
build:
DO NOT KNOW HOW TO DO IT
I am checking some templates from Gitlab's website and found one for Docker:
# This file is a template, and might need editing before it works on your project.
# Official docker image.
image: docker:latest
services:
- docker:dind
before_script:
- docker login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" $CI_REGISTRY
build-master:
stage: build
script:
- docker build --pull -t "$CI_REGISTRY_IMAGE" .
- docker push "$CI_REGISTRY_IMAGE"
only:
- master
build:
stage: build
script:
- docker build --pull -t "$CI_REGISTRY_IMAGE:$CI_COMMIT_REF_SLUG" .
- docker push "$CI_REGISTRY_IMAGE:$CI_COMMIT_REF_SLUG"
except:
- master
However, both of these do not work for me because I need to have python for testing and docker for building the image. Is there way to do it with Gitlab CI without creating a custom Docker image that has both python and Docker installed?

Answer 1

I found out that I can create multiple jobs, each with their own images:
stages:
- test
- build
test:
stage: test
image: python:3.7-slim
variables:
DJANGO_SECRET_KEY: key
before_script:
- pip3 install -r requirements.txt
script:
- python manage.py test
only:
- master
build:
stage: build
image: docker:latest
services:
- docker:dind
before_script:
- docker login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" $CI_REGISTRY
script:
- docker build --pull -t "$CI_REGISTRY_IMAGE" .
- docker push "$CI_REGISTRY_IMAGE"
only:
- master