Run tests Docker in Docker (#261)

* Try running tests in Docker

* Spawn new container for each test

* Store test artifacts outside of mount

* When requested, build up to date image in test script

* sudo is unneccessary in containerized test env

* Skip azure test

* Backdate fixture file in JSON database

* Pin versions for azure tools

* Mount temp volume for /var/lib/docker to prevent dangling ones created by VOLUME instruction

* Fail backdating tests with message

* Add some documentation on test setup

* Cache images

* Run compose stacks with shortened default timeout

.github/workflows/test.yml

@@ -15,16 +15,7 @@ jobs:
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v2
 
-      - name: Build Docker Image
-        env:
-          DOCKER_BUILDKIT: '1'
-        run: docker build . -t offen/docker-volume-backup:test
-
       - name: Run Tests
         working-directory: ./test
         run: |
-          # Stop the buildx container so the tests can make assertions
-          # about the number of running containers
-          docker rm -f $(docker ps -aq)
-          export GPG_TTY=$(tty)
-          ./test.sh test
+          BUILD_IMAGE=1 ./test.sh