diff --git a/nginx/Makefile b/nginx/Makefile
index 4ab7f23..d43ffa6 100644
--- a/nginx/Makefile
+++ b/nginx/Makefile
@@ -1,2 +1,8 @@
 PARENT_DIR := ..
 include $(PARENT_DIR)/Makefile
+
+.PHONY: test
+
+test: uninstall clean install
+	@echo "Running Nginx tests..."
+	curl -sSfL -I http://localhost/
diff --git a/nginx/README.md b/nginx/README.md
index db9de21..3c8e209 100644
--- a/nginx/README.md
+++ b/nginx/README.md
@@ -52,3 +52,9 @@ Finally, remove the quadlets, their configuration and their data.
 ```sh
 sudo make uninstall clean
 ```
+
+## Integration tests
+
+```sh
+sudo make test
+```
diff --git a/postgresql/Makefile b/postgresql/Makefile
index 4ab7f23..c4744e1 100644
--- a/postgresql/Makefile
+++ b/postgresql/Makefile
@@ -1,2 +1,39 @@
 PARENT_DIR := ..
 include $(PARENT_DIR)/Makefile
+
+.PHONY: test test-set-pgmajor
+
+PG_MAJOR_START ?= 14
+PG_MAJOR_LAST ?= 18
+test-set-pgmajor:
+	sed -i 's/^PG_MAJOR=.*/PG_MAJOR=$(PG_MAJOR_START)/' config/config.env
+
+test: uninstall clean test-set-pgmajor install
+	@echo "Running PostgreSQL integration tests..."; \
+	set -Eeuo pipefail; \
+	sleep 2; \
+	echo "Creating a test database and a witness table..."; \
+	podman exec postgresql-server su postgres -c "createdb test"; \
+	podman exec postgresql-server su postgres -c "psql -U postgres -d test -c \"CREATE TABLE witness (id SERIAL PRIMARY KEY, version VARCHAR); INSERT INTO witness (version) SELECT version();\""; \
+	podman exec postgresql-server su postgres -c "psql -U postgres -d test -c \"SELECT * FROM witness;\""; \
+	for (( ver=$(PG_MAJOR_START); ver<$(PG_MAJOR_LAST); ver++ )); do \
+		echo "Running a backup..."; \
+		nextver=$$(($$ver + 1)); \
+		systemctl start postgresql-backup.service; \
+		systemctl stop postgresql.target; \
+		sleep 1; \
+		rm -rf /var/lib/quadlets/postgresql/{$$ver,$$nextver,data,latest,.initialized}; \
+		echo "Restoring the backup to PostgreSQL $$ver..."; \
+		systemctl start postgresql.target; \
+		sleep 2; \
+		podman exec postgresql-server su postgres -c "psql -U postgres -d test -c \"SELECT * FROM witness;\""; \
+		echo "Testing upgrade from PostgreSQL $$ver to $$nextver..."; \
+		systemctl stop postgresql.target; \
+		sed -i "s/^PG_MAJOR=.*/PG_MAJOR=$$nextver/" /etc/quadlets/postgresql/config.env; \
+		systemctl start postgresql.target; \
+		sleep 2; \
+		echo "Inserting line into the witness table..."; \
+		podman exec postgresql-server su postgres -c "psql -U postgres -d test -c \"INSERT INTO witness (version) SELECT version();\""; \
+	done; \
+	podman exec postgresql-server su postgres -c "psql -U postgres -d test -c \"SELECT * FROM witness;\""; \
+	echo "PostgreSQL upgrade tests completed."
diff --git a/postgresql/README.md b/postgresql/README.md
index 173d01c..09ea108 100644
--- a/postgresql/README.md
+++ b/postgresql/README.md
@@ -96,3 +96,9 @@ Finally, remove the quadlets, their configuration and their data.
 ```sh
 sudo make uninstall clean
 ```
+
+## Integration tests
+
+```sh
+sudo make test
+```
diff --git a/postgresql/config/config.env b/postgresql/config/config.env
index 24278f6..7cd2fe1 100644
--- a/postgresql/config/config.env
+++ b/postgresql/config/config.env
@@ -4,5 +4,5 @@ POSTGRES_DB=postgres
 POSTGRES_HOST_AUTH_METHOD=scram-sha-256
 POSTGRES_INITDB_ARGS=--auth-host=scram-sha-256
 PGPORT=5432
-PG_MAJOR=17
+PG_MAJOR=14
 POSTGRES_BACKUP_RETENTION=7
diff --git a/postgresql/config/init.sh b/postgresql/config/init.sh
index 204db76..5e62160 100755
--- a/postgresql/config/init.sh
+++ b/postgresql/config/init.sh
@@ -2,6 +2,12 @@
 
 set -Eeuo pipefail
 
+echo "PostgreSQL binaries version:"
+postgres --version
+echo
+echo "PostgreSQL data directory: $PGDATA"
+echo
+
 last_backup=""
 for f in /var/lib/postgresql/backup/*/backup_manifest; do
   # If there are no backups, the glob pattern above won't match any files
diff --git a/postgresql/config/upgrade.sh b/postgresql/config/upgrade.sh
new file mode 100755
index 0000000..d1d3d8f
--- /dev/null
+++ b/postgresql/config/upgrade.sh
@@ -0,0 +1,149 @@
+#!/bin/bash
+
+set -Eeuo pipefail
+
+# Find the latest PostgreSQL data directory
+SOURCE_PGDATA=""
+last_version=""
+for version_file in /var/lib/postgresql/*/docker/PG_VERSION; do
+  if [ -f "$version_file" ]; then
+    version_dir=$(dirname "$version_file")
+    version_major=$(cat "$version_file")
+    if [ -z "$last_version" ] || [ "$version_major" -gt "$last_version" ]; then
+      last_version="$version_major"
+      SOURCE_PGDATA="$version_dir"
+    fi
+  fi
+done
+if [ -z "$SOURCE_PGDATA" ] || [ ! -d "$SOURCE_PGDATA" ]; then
+  echo "No PostgreSQL data directory found."
+  exit 1
+fi
+echo "Using PostgreSQL data directory: $SOURCE_PGDATA"
+
+# Upgrade destination
+TARGET_MAJOR_VERSION=${PGTARGET%%.*}
+TARGET_PATH="/usr/local/bin/"
+TARGET_PGDATA="/var/lib/postgresql/${TARGET_MAJOR_VERSION}/docker"
+
+# Upgrade source
+SOURCE_MAJOR_VERSION=$(cat "${SOURCE_PGDATA}/PG_VERSION")
+SOURCE_PATH="/usr/local-pg${SOURCE_MAJOR_VERSION}/bin"
+
+# Reuse functions from the official entrypoint script
+source /usr/local/bin/postgres-docker-entrypoint.sh
+
+# Because they may have been over by the sourced script, reset all flags
+set -Eeuo pipefail
+
+# if first arg looks like a flag, assume we want to run postgres server
+if [ "$#" -eq 0 ] || [ "${1:0:1}" = '-' ]; then
+  set -- postgres "$@"
+fi
+
+# Setup environment variables
+docker_setup_env
+
+##
+## Sanity checks
+##
+
+# No need to upgrade if same major version
+if [ "${SOURCE_MAJOR_VERSION}" == "${TARGET_MAJOR_VERSION}" ]; then
+  echo "PostgreSQL data files version matches target version. No upgrade required."
+  exit 0
+fi
+# No automatic upgrade support for PostgreSQL versions less than 14
+if [ "${SOURCE_MAJOR_VERSION}" -lt 14 ]; then
+  echo "PosgreSQL <14 is no longer supported for automatic upgrade. Please perform a manual upgrade."
+  exit 1
+fi
+# No downgrade support
+if [ "${SOURCE_MAJOR_VERSION}" -gt "${TARGET_MAJOR_VERSION}" ]; then
+  echo "Downgrades are not supported. Aborting."
+  exit 1
+fi
+# Check for concurrent upgrade processes
+if [ -f "${SOURCE_PGDATA}/upgrade_in_progress.lock" ]; then
+  echo "Another upgrade process seems to be running (upgrade_in_progress.lock file found). Aborting."
+  exit 2
+fi
+
+# On PG v18, we have to check that data checksums, be it positive or negative, is set on the initdb args
+# even when the user already provided initdb args, because otherwise Postgres v18 assumes you want checksums
+# we now do this on every version to avoid one more conditional
+# it also adds support for people who used Postgres with checksums before v18
+if [[ -z "${POSTGRES_INITDB_ARGS:-}" || "${POSTGRES_INITDB_ARGS:-}" != *"data-checksums"* ]]; then
+  DATA_CHECKSUMS_ENABLED=$(echo 'SHOW DATA_CHECKSUMS' | "${SOURCE_PATH}/postgres" --single "${@:2}" -D "${SOURCE_PGDATA}" "${POSTGRES_DB}" | grep 'data_checksums = "' | cut -d '"' -f 2)
+
+  if [ "$DATA_CHECKSUMS_ENABLED" == "on" ]; then
+    DATA_CHECKSUMS_PARAMETER="--data-checksums"
+  elif [ "$TARGET_MAJOR_VERSION" -eq 18 ]; then
+    # Postgres v18 enables data checksums by default and is the only version with this opt-out parameter
+    DATA_CHECKSUMS_PARAMETER="--no-data-checksums"
+  fi
+  POSTGRES_INITDB_ARGS="${POSTGRES_INITDB_ARGS:-} ${DATA_CHECKSUMS_PARAMETER:-}"
+fi
+
+# Flags the data directory as being in the middle of an upgrade
+mkdir -p "${TARGET_PGDATA}"
+touch "${SOURCE_PGDATA}/upgrade_in_progress.lock"
+
+# Now PGDATA points to the target data directory
+export PGDATA="${TARGET_PGDATA}"
+
+# Initialize target data directory
+docker_verify_minimum_env
+docker_init_database_dir
+
+# Change into the PostgreSQL database directory, to avoid a pg_upgrade error about write permissions
+cd "${PGDATA}"
+
+# Perform the upgrade
+echo "Upgrading PostgreSQL from version ${SOURCE_MAJOR_VERSION} to ${TARGET_MAJOR_VERSION}..."
+"${TARGET_PATH}/pg_upgrade" --username="${POSTGRES_USER}" --link \
+  --old-datadir "${SOURCE_PGDATA}" --new-datadir "${TARGET_PGDATA}" \
+  --old-bindir "${SOURCE_PATH}" --new-bindir "${TARGET_PATH}" \
+  --socketdir="/var/run/postgresql" \
+  --old-options "${run_options[*]}" --new-options "${run_options[*]}"
+
+# Re-use the pg_hba.conf and pg_ident.conf from the old data directory
+cp -f "${SOURCE_PGDATA}/pg_hba.conf" "${SOURCE_PGDATA}/pg_ident.conf" "${TARGET_PGDATA}"
+
+# Set PGPASSWORD in case password authentication is used
+if [ -z "${PGPASSWORD:-}" ] && [ -n "${POSTGRES_PASSWORD:-}" ]; then
+  export PGPASSWORD="${POSTGRES_PASSWORD}"
+fi
+
+# Start a temporary PostgreSQL server
+docker_temp_server_start "$@"
+
+if [ -n "${POSTGRES_UPDATE_SCRIPT:-}" ] && [ -f "${POSTGRES_UPDATE_SCRIPT}" ]; then
+  echo "Running update script: ${POSTGRES_UPDATE_SCRIPT}"
+  psql --username="${POSTGRES_USER}" -f "${POSTGRES_UPDATE_SCRIPT}"
+fi
+
+echo "Updating query planner stats"
+declare -a database_list=( $(echo 'SELECT datname FROM pg_catalog.pg_database WHERE datistemplate IS FALSE' | psql --username="${POSTGRES_USER}" -1t --csv "${POSTGRES_DB}") )
+for database in "${database_list[@]}"; do
+  echo "VACUUM (ANALYZE, VERBOSE, INDEX_CLEANUP FALSE)" | psql --username="${POSTGRES_USER}" -t --csv "${database}"
+done
+
+if [[ "${PGAUTO_REINDEX:-}" != "no" ]]; then
+  echo "Reindexing the databases"
+
+  if [[ "$TARGET_MAJOR_VERSION" -le 15 ]]; then
+    reindexdb --all --username="${POSTGRES_USER}"
+  else
+    reindexdb --all --concurrently --username="${POSTGRES_USER}"
+  fi
+  echo "End of reindexing the databases"
+fi
+
+# Stop the temporary PostgreSQL server
+unset PGPASSWORD
+docker_temp_server_stop
+
+# Clean up lock files
+rm -f "${SOURCE_PGDATA}/upgrade_in_progress.lock"
+echo "PostgreSQL upgrade from version ${SOURCE_MAJOR_VERSION} to ${TARGET_MAJOR_VERSION} completed successfully."
diff --git a/postgresql/postgresql-init.container b/postgresql/postgresql-init.container
index 4852b57..18bf6cb 100644
--- a/postgresql/postgresql-init.container
+++ b/postgresql/postgresql-init.container
@@ -26,7 +26,7 @@ Environment=PGDATA=/var/lib/postgresql/${PG_MAJOR}/docker
 # Those environment variables will be injected by podman into the container
 EnvironmentFile=/etc/quadlets/postgresql/config.env
 
-# Use the official entrypoint script to initialize the database
+# Use our entrypoint script to initialize the database
 Entrypoint=/usr/local/bin/init.sh
 
 # Volume mounts
diff --git a/postgresql/postgresql-upgrade.container b/postgresql/postgresql-upgrade.container
index d1f2036..9ac0a94 100644
--- a/postgresql/postgresql-upgrade.container
+++ b/postgresql/postgresql-upgrade.container
@@ -22,15 +22,16 @@ Image=docker.io/pgautoupgrade/pgautoupgrade:${PG_MAJOR}-alpine
 # Network configuration
 Network=host
 
-# PostgreSQL storage is specific to major version
-Environment=PGDATA=/var/lib/postgresql/${PG_MAJOR}/docker
-Environment=PGAUTO_ONESHOT=yes
-
 # Those environment variables will be injected by podman into the container
 EnvironmentFile=/etc/quadlets/postgresql/config.env
 
+# Use our entrypoint script to upgrade the database
+Entrypoint=/usr/local/bin/upgrade.sh
+User=postgres
+
 # Volume mounts
 Volume=/var/lib/quadlets/postgresql:/var/lib/postgresql:z
+Volume=/etc/quadlets/postgresql/upgrade.sh:/usr/local/bin/upgrade.sh:z,ro
 
 [Service]
 Restart=no