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

test/zstd/run.sh

@@ -9,7 +9,7 @@ current_test=$(basename $(pwd))
 docker network create test_network
 docker volume create app_data
 
-mkdir -p local
+LOCAL_DIR=$(mktemp -d)
 
 docker run -d -q \
   --name offen \
@@ -22,7 +22,7 @@ sleep 10
 docker run --rm -q \
   --network test_network \
   -v app_data:/backup/app_data \
-  -v ./local:/archive \
+  -v $LOCAL_DIR:/archive \
   -v /var/run/docker.sock:/var/run/docker.sock \
   --env BACKUP_COMPRESSION=zst \
   --env BACKUP_FILENAME='test.{{ .Extension }}' \
@@ -30,7 +30,7 @@ docker run --rm -q \
   offen/docker-volume-backup:${TEST_VERSION:-canary}
 
 tmp_dir=$(mktemp -d)
-tar -xvf ./local/test.tar.zst --zstd -C $tmp_dir
+tar -xvf "$LOCAL_DIR/test.tar.zst" --zstd -C $tmp_dir
 if [ ! -f "$tmp_dir/backup/app_data/offen.db" ]; then
   fail "Could not find expected file in untared archive."
 fi
@@ -39,8 +39,3 @@ pass "Found relevant files in untared local backup."
 # This test does not stop containers during backup. This is happening on
 # purpose in order to cover this setup as well.
 expect_running_containers "1"
-
-docker rm $(docker stop offen)
-
-docker volume rm app_data
-docker network rm test_network