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/extend/docker-compose.yml

@@ -11,7 +11,7 @@ services:
       BACKUP_CRON_EXPRESSION: 0 0 5 31 2 ?
       EXEC_FORWARD_OUTPUT: "true"
     volumes:
-      - ./local:/local
+      - ${LOCAL_DIR:-local}:/local
       - app_data:/backup/app_data:ro
       - /var/run/docker.sock:/var/run/docker.sock
 

test/extend/run.sh

@@ -6,7 +6,7 @@ cd "$(dirname "$0")"
 . ../util.sh
 current_test=$(basename $(pwd))
 
-mkdir -p local
+export LOCAL_DIR=$(mktemp -d)
 
 export BASE_VERSION="${TEST_VERSION:-canary}"
 export TEST_VERSION="${TEST_VERSION:-canary}-with-rsync"
@@ -22,8 +22,6 @@ sleep 5
 
 expect_running_containers "2"
 
-if [ ! -f "./local/app_data/offen.db" ]; then
+if [ ! -f "$LOCAL_DIR/app_data/offen.db" ]; then
   fail "Could not find expected file in untared archive."
 fi
-
-docker compose down --volumes