Simplify mocking of mqqt client

This way we do not have scope imports from loaders.mqtt to the test body.

tests/loaders/test_mqtt.py

@@ -1,7 +1,6 @@
 from __future__ import annotations
 
 import argparse
-import sys
 import time
 from dataclasses import dataclass
 from struct import pack
@@ -11,6 +10,7 @@
 import pytest
 
 from dissect.target import Target
+from dissect.target.loaders.mqtt import Broker, MQTTConnection, case, host_name
 
 
 class MQTTMock(MagicMock):
@@ -69,21 +69,10 @@ def read(self, *args) -> MockSeekMessage | None:
 
 
 @pytest.fixture
-def mock_paho(monkeypatch: pytest.MonkeyPatch) -> Iterator[MagicMock]:
-    with monkeypatch.context() as m:
-        mock_paho = MagicMock()
-        m.setitem(sys.modules, "paho", mock_paho)
-        m.setitem(sys.modules, "paho.mqtt", mock_paho.mqtt)
-        m.setitem(sys.modules, "paho.mqtt.client", mock_paho.mqtt.client)
+def mock_client(monkeypatch: pytest.MonkeyPatch) -> None:
+    import paho.mqtt.client as mqtt
 
-        yield mock_paho
-
-
-@pytest.fixture
-def mock_client(mock_paho: MagicMock) -> Iterator[MagicMock]:
-    mock_client = MQTTMock()
-    mock_paho.mqtt.client.Client.return_value = mock_client
-    yield mock_client
+    monkeypatch.setattr(mqtt, "Client", MQTTMock)
 
 
 @pytest.fixture
@@ -104,7 +93,7 @@ def mock_broker() -> Iterator[MockBroker]:
 @patch.object(time, "sleep")  # improve speed during test, no need to wait for peers
 def test_remote_loader_stream(
     time: MagicMock,
-    mock_client: MagicMock,
+    mock_client: None,
     alias: str,
     hosts: list[str],
     disks: list[int],
@@ -113,8 +102,6 @@ def test_remote_loader_stream(
     read: int,
     expected: bytes,
 ) -> None:
-    from dissect.target.loaders.mqtt import Broker
-
     broker = Broker("0.0.0.0", "1884", "key", "crt", "ca", "case1", "user", "pass")
     broker.connect()
     broker.mqtt_client.fill_disks(disks)
@@ -134,8 +121,6 @@ def test_remote_loader_stream(
 
 
 def test_mqtt_loader_prefetch(mock_broker: MockBroker) -> None:
-    from dissect.target.loaders.mqtt import MQTTConnection
-
     connection = MQTTConnection(mock_broker, "")
     connection.prefetch_factor_inc = 10
     assert connection.factor == 1
@@ -174,6 +159,7 @@ def generate_longest_valid_hostname():
         ("example-label.com", True),
         ("example..com", False),
         (generate_longest_valid_hostname(), True),
+        (generate_longest_valid_hostname() + 'a', False),
     ],
     ids=[
         "valid_domain",
@@ -188,11 +174,10 @@ def generate_longest_valid_hostname():
         "valid_domain_with_hyphen",
         "invalid_empty_label",
         "valid_max_length",
+        "too_long"
     ],
 )
 def test_host_name_parser(hostname: str, is_valid_hostname: bool) -> None:
-    from dissect.target.loaders.mqtt import host_name
-
     assert host_name(hostname) == is_valid_hostname
 
 
@@ -220,8 +205,6 @@ def test_host_name_parser(hostname: str, is_valid_hostname: bool) -> None:
     ],
 )
 def test_case(case_name, parse_result: str | pytest.RaisesContext[argparse.ArgumentTypeError]) -> None:
-    from dissect.target.loaders.mqtt import case
-
     if isinstance(parse_result, str):
         assert case(case_name) == parse_result
     else: