diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index f95d77bca..d1bf39215 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -77,6 +77,7 @@ jobs:
           - tls-integration
           - standalone-integration
           - legacy-client-relation-integration
+          - upgrade-integration
         agent-versions: 
           - "2.9.45"  # renovate: latest juju 2
           - "3.1.5"  # renovate: latest juju 3
diff --git a/tests/integration/test_upgrade.py b/tests/integration/test_upgrade.py
new file mode 100644
index 000000000..2660f1035
--- /dev/null
+++ b/tests/integration/test_upgrade.py
@@ -0,0 +1,112 @@
+#!/usr/bin/env python3
+# Copyright 2023 Canonical Ltd.
+# See LICENSE file for licensing details.
+import asyncio
+import logging
+
+import pytest
+from pytest_operator.plugin import OpsTest
+
+from constants import BACKEND_RELATION_NAME
+
+from .helpers.helpers import (
+    CHARM_SERIES,
+    PG,
+    PGB,
+    PGB_METADATA,
+)
+from .relations.pgbouncer_provider.helpers import check_new_relation
+
+logger = logging.getLogger(__name__)
+
+CLIENT_APP_NAME = "postgresql-test-app"
+SECONDARY_CLIENT_APP_NAME = "secondary-application"
+DATA_INTEGRATOR_APP_NAME = "data-integrator"
+PGB_RESOURCES = {
+    "pgbouncer-image": PGB_METADATA["resources"]["pgbouncer-image"]["upstream-source"]
+}
+APP_NAMES = [CLIENT_APP_NAME, PG, PGB]
+FIRST_DATABASE_RELATION_NAME = "first-database"
+APPLICATION_FIRST_DBNAME = "postgresql_test_app_first_database"
+
+
+@pytest.mark.abort_on_fail
+async def test_in_place_upgrade(ops_test: OpsTest, pgb_charm):
+    """Test basic functionality of database relation interface."""
+    # Deploy both charms (multiple units for each application to test that later they correctly
+    # set data in the relation application databag using only the leader unit).
+    logger.info("Deploying PGB...")
+    await asyncio.gather(
+        ops_test.model.deploy(
+            CLIENT_APP_NAME,
+            application_name=CLIENT_APP_NAME,
+            series=CHARM_SERIES,
+            channel="edge",
+        ),
+        ops_test.model.deploy(
+            pgb_charm,
+            resources=PGB_RESOURCES,
+            application_name=PGB,
+            num_units=2,
+            series=CHARM_SERIES,
+            trust=True,
+        ),
+        ops_test.model.deploy(
+            PG,
+            application_name=PG,
+            num_units=2,
+            channel="14/edge",
+            trust=True,
+        ),
+    )
+    await ops_test.model.add_relation(f"{PGB}:{BACKEND_RELATION_NAME}", f"{PG}:database")
+
+    async with ops_test.fast_forward():
+        await ops_test.model.wait_for_idle(apps=[PGB, PG], status="active")
+
+    # Relate the charms and wait for them exchanging some connection data.
+    global client_relation
+    client_relation = await ops_test.model.add_relation(
+        f"{CLIENT_APP_NAME}:{FIRST_DATABASE_RELATION_NAME}", PGB
+    )
+
+    async with ops_test.fast_forward():
+        await ops_test.model.wait_for_idle(apps=APP_NAMES, status="active", raise_on_blocked=True)
+
+    # This test hasn't passed if we can't pass a tiny amount of data through the new relation
+    await check_new_relation(
+        ops_test,
+        unit_name=ops_test.model.applications[CLIENT_APP_NAME].units[0].name,
+        relation_id=client_relation.id,
+        dbname=APPLICATION_FIRST_DBNAME,
+        relation_name=FIRST_DATABASE_RELATION_NAME,
+    )
+
+    leader = None
+    for unit in ops_test.model.applications[PGB].units:
+        if await unit.is_leader_from_status():
+            leader = unit
+            break
+
+    action = await leader.run_action("pre-upgrade-check")
+    await action.wait()
+
+    await ops_test.model.wait_for_idle(apps=APP_NAMES, status="active", raise_on_blocked=True)
+
+    logger.info("Upgrading last PGB...")
+    await ops_test.model.applications[PGB].refresh(path=pgb_charm)
+    await ops_test.model.wait_for_idle(apps=[PGB], status="active", raise_on_blocked=True)
+
+    logger.info("Resuming upgrade...")
+    action = await leader.run_action("resume-upgrade")
+    await action.wait()
+
+    await ops_test.model.wait_for_idle(apps=[PGB], status="active", raise_on_blocked=True)
+
+    await check_new_relation(
+        ops_test,
+        unit_name=ops_test.model.applications[CLIENT_APP_NAME].units[0].name,
+        relation_id=client_relation.id,
+        dbname=APPLICATION_FIRST_DBNAME,
+        relation_name=FIRST_DATABASE_RELATION_NAME,
+    )
diff --git a/tox.ini b/tox.ini
index 3515a0bd6..bbec35066 100644
--- a/tox.ini
+++ b/tox.ini
@@ -132,6 +132,17 @@ commands =
     pip install juju=={env:LIBJUJU}
     poetry run pytest -v --tb native --log-cli-level=INFO -s --durations=0 {posargs} {[vars]tests_path}/integration/test_tls.py
 
+[testenv:upgrade-integration-{juju2, juju3}]
+description = Run upgrade integration tests
+pass_env =
+    {[testenv]pass_env}
+    CI
+    CI_PACKED_CHARMS
+commands =
+    poetry install --with integration
+    pip install juju=={env:LIBJUJU}
+    poetry run pytest -v --tb native --log-cli-level=INFO -s --durations=0 {posargs} {[vars]tests_path}/integration/test_upgrade.py
+
 [testenv:poetry-lock]
 description = Install, lock and export poetry dependencies
 commands =