diff --git a/scenario/context.py b/scenario/context.py
index cb5331d5..26665c06 100644
--- a/scenario/context.py
+++ b/scenario/context.py
@@ -9,7 +9,6 @@
 from typing import TYPE_CHECKING, Any, Dict, List, Mapping, Optional, Type, Union, cast
 
 import ops
-import ops.testing
 
 from scenario.errors import AlreadyEmittedError, ContextSetupError
 from scenario.logger import logger as scenario_logger
@@ -28,8 +27,20 @@
 )
 
 if TYPE_CHECKING:  # pragma: no cover
+    try:
+        from ops._private.harness import ExecArgs  # type: ignore
+    except ImportError:
+        from ops.testing import ExecArgs  # type: ignore
+
     from scenario.ops_main_mock import Ops
-    from scenario.state import AnyJson, JujuLogLine, RelationBase, State, _EntityStatus
+    from scenario.state import (
+        AnyJson,
+        CharmType,
+        JujuLogLine,
+        RelationBase,
+        State,
+        _EntityStatus,
+    )
 
 logger = scenario_logger.getChild("runtime")
 
@@ -426,7 +437,7 @@ def test_foo():
 
     def __init__(
         self,
-        charm_type: Type[ops.testing.CharmType],
+        charm_type: Type["CharmType"],
         meta: Optional[Dict[str, Any]] = None,
         *,
         actions: Optional[Dict[str, Any]] = None,
@@ -491,7 +502,7 @@ def __init__(
         self.charm_root = charm_root
         self.juju_version = juju_version
         if juju_version.split(".")[0] == "2":
-            logger.warn(
+            logger.warning(
                 "Juju 2.x is closed and unsupported. You may encounter inconsistencies.",
             )
 
@@ -508,7 +519,7 @@ def __init__(
         self.juju_log: List["JujuLogLine"] = []
         self.app_status_history: List["_EntityStatus"] = []
         self.unit_status_history: List["_EntityStatus"] = []
-        self.exec_history: Dict[str, List[ops.testing.ExecArgs]] = {}
+        self.exec_history: Dict[str, List["ExecArgs"]] = {}
         self.workload_version_history: List[str] = []
         self.removed_secret_revisions: List[int] = []
         self.emitted_events: List[ops.EventBase] = []
@@ -644,7 +655,10 @@ def run(self, event: "_Event", state: "State") -> "State":
         assert self._output_state is not None
         if event.action:
             if self._action_failure_message is not None:
-                raise ActionFailed(self._action_failure_message, self._output_state)
+                raise ActionFailed(
+                    self._action_failure_message,
+                    state=self._output_state,
+                )
         return self._output_state
 
     @contextmanager
diff --git a/scenario/mocking.py b/scenario/mocking.py
index 9e004af4..def3c395 100644
--- a/scenario/mocking.py
+++ b/scenario/mocking.py
@@ -1,7 +1,9 @@
 #!/usr/bin/env python3
 # Copyright 2023 Canonical Ltd.
 # See LICENSE file for licensing details.
+
 import datetime
+import io
 import shutil
 from pathlib import Path
 from typing import (
@@ -20,6 +22,12 @@
 )
 
 from ops import JujuVersion, pebble
+
+try:
+    from ops._private.harness import ExecArgs, _TestingPebbleClient  # type: ignore
+except ImportError:
+    from ops.testing import ExecArgs, _TestingPebbleClient  # type: ignore
+
 from ops.model import CloudSpec as CloudSpec_Ops
 from ops.model import ModelError
 from ops.model import Port as Port_Ops
@@ -33,7 +41,6 @@
     _ModelBackend,
 )
 from ops.pebble import Client, ExecError
-from ops.testing import ExecArgs, _TestingPebbleClient
 
 from scenario.errors import ActionMissingFromContextError
 from scenario.logger import logger as scenario_logger
@@ -66,9 +73,9 @@ def __init__(
         change_id: int,
         args: ExecArgs,
         return_code: int,
-        stdin: Optional[TextIO],
-        stdout: Optional[TextIO],
-        stderr: Optional[TextIO],
+        stdin: Optional[Union[TextIO, io.BytesIO]],
+        stdout: Optional[Union[TextIO, io.BytesIO]],
+        stderr: Optional[Union[TextIO, io.BytesIO]],
     ):
         self._change_id = change_id
         self._args = args
@@ -99,7 +106,12 @@ def wait_output(self):
         stdout = self.stdout.read() if self.stdout is not None else None
         stderr = self.stderr.read() if self.stderr is not None else None
         if self._return_code != 0:
-            raise ExecError(list(self._args.command), self._return_code, stdout, stderr)
+            raise ExecError(
+                list(self._args.command),
+                self._return_code,
+                stdout,  # type: ignore
+                stderr,  # type: ignore
+            )
         return stdout, stderr
 
     def send_signal(self, sig: Union[int, str]):  # noqa: U100
@@ -167,15 +179,18 @@ def get_pebble(self, socket_path: str) -> "Client":
             # container not defined in state.
             mounts = {}
 
-        return _MockPebbleClient(
-            socket_path=socket_path,
-            container_root=container_root,
-            mounts=mounts,
-            state=self._state,
-            event=self._event,
-            charm_spec=self._charm_spec,
-            context=self._context,
-            container_name=container_name,
+        return cast(
+            Client,
+            _MockPebbleClient(
+                socket_path=socket_path,
+                container_root=container_root,
+                mounts=mounts,
+                state=self._state,
+                event=self._event,
+                charm_spec=self._charm_spec,
+                context=self._context,
+                container_name=container_name,
+            ),
         )
 
     def _get_relation_by_id(self, rel_id) -> "RelationBase":
@@ -616,7 +631,7 @@ def storage_add(self, name: str, count: int = 1):
             )
 
         if "/" in name:
-            # this error is raised by ops.testing but not by ops at runtime
+            # this error is raised by Harness but not by ops at runtime
             raise ModelError('storage name cannot contain "/"')
 
         self._context.requested_storages[name] = count
@@ -752,6 +767,10 @@ def __init__(
 
         self._root = container_root
 
+        self._notices: Dict[Tuple[str, str], pebble.Notice] = {}
+        self._last_notice_id = 0
+        self._changes: Dict[str, pebble.Change] = {}
+
         # load any existing notices and check information from the state
         self._notices: Dict[Tuple[str, str], pebble.Notice] = {}
         self._check_infos: Dict[str, pebble.CheckInfo] = {}
@@ -790,7 +809,7 @@ def _layers(self) -> Dict[str, pebble.Layer]:
     def _service_status(self) -> Dict[str, pebble.ServiceStatus]:
         return self._container.service_statuses
 
-    # Based on a method of the same name from ops.testing.
+    # Based on a method of the same name from Harness.
     def _find_exec_handler(self, command) -> Optional["Exec"]:
         handlers = {exec.command_prefix: exec for exec in self._container.execs}
         # Start with the full command and, each loop iteration, drop the last
diff --git a/scenario/runtime.py b/scenario/runtime.py
index f4df73db..92cfcae7 100644
--- a/scenario/runtime.py
+++ b/scenario/runtime.py
@@ -38,10 +38,8 @@
 )
 
 if TYPE_CHECKING:  # pragma: no cover
-    from ops.testing import CharmType
-
     from scenario.context import Context
-    from scenario.state import State, _CharmSpec, _Event
+    from scenario.state import CharmType, State, _CharmSpec, _Event
 
 logger = scenario_logger.getChild("runtime")
 STORED_STATE_REGEX = re.compile(
diff --git a/scenario/state.py b/scenario/state.py
index 9179735d..b089c582 100644
--- a/scenario/state.py
+++ b/scenario/state.py
@@ -117,7 +117,7 @@
 class ActionFailed(Exception):
     """Raised at the end of the hook if the charm has called ``event.fail()``."""
 
-    def __init__(self, message: str, state: "State"):
+    def __init__(self, message: str, *, state: "State"):
         self.message = message
         self.state = state
 
diff --git a/tests/helpers.py b/tests/helpers.py
index 5ceffa9d..49ffaeff 100644
--- a/tests/helpers.py
+++ b/tests/helpers.py
@@ -18,9 +18,7 @@
 from scenario.context import _DEFAULT_JUJU_VERSION, Context
 
 if TYPE_CHECKING:  # pragma: no cover
-    from ops.testing import CharmType
-
-    from scenario.state import State, _Event
+    from scenario.state import CharmType, State, _Event
 
     _CT = TypeVar("_CT", bound=Type[CharmType])
 
diff --git a/tests/test_charm_spec_autoload.py b/tests/test_charm_spec_autoload.py
index 57b93a31..b9da4d24 100644
--- a/tests/test_charm_spec_autoload.py
+++ b/tests/test_charm_spec_autoload.py
@@ -1,18 +1,15 @@
 import importlib
 import sys
-import tempfile
 from contextlib import contextmanager
 from pathlib import Path
 from typing import Type
 
 import pytest
 import yaml
-from ops import CharmBase
-from ops.testing import CharmType
 
 from scenario import Context, Relation, State
 from scenario.context import ContextSetupError
-from scenario.state import MetadataNotFoundError, _CharmSpec
+from scenario.state import CharmType, MetadataNotFoundError, _CharmSpec
 
 CHARM = """
 from ops import CharmBase