- new variable

.gitlab-ci.yml

 variables:
   VERAPDF_VERSION: "1.24.1"
   DOCKERFILE_DEB: "${CI_PROJECT_DIR}/gitlab-ci/Dockerfile_DEB"
+  IMAGE_BASE_DEB: "sdvharbor.slub-dresden.de/replication/debian:bookworm-slim"
   IMAGE_TARGET_DEB: "${CI_REGISTRY_IMAGE}/debian12_verapdf_build_env"
   INSTALL_PATH_DEB: "/usr/local/verapdf"
 
@@ -110,7 +111,7 @@ test-install-debian-job:
   timeout: 5m
   image:
     # HINT: debian base image to simulate an installation target
-    name: "sdvharbor.slub-dresden.de/replication/debian:bookworm-slim"
+    name: "${IMAGE_BASE_DEB}"
   tags:
     - "docker"
   script: