diff --git a/testing/__init__.py b/testing/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/testing/test_app.py b/testing/test_app.py
new file mode 100644
index 0000000..50d84f8
--- /dev/null
+++ b/testing/test_app.py
@@ -0,0 +1,8 @@
+from packaging.version import Version
+from packaging.version import parse as parse_version
+
+from pytest_mqtt import __version__
+
+
+def test_app_version():
+    assert isinstance(parse_version(__version__), Version)
diff --git a/testing/test_capmqtt.py b/testing/test_capmqtt.py
new file mode 100644
index 0000000..88fd4c4
--- /dev/null
+++ b/testing/test_capmqtt.py
@@ -0,0 +1,15 @@
+from pytest_mqtt.capmqtt import MqttClientAdapter
+from pytest_mqtt.util import delay
+
+
+def test_mqtt_client_adapter(mosquitto):
+    mqtt_client = MqttClientAdapter()
+    mqtt_client.start()
+
+    # Submit MQTT message.
+    message_info = mqtt_client.publish("foo", "bar")
+    message_info.wait_for_publish(timeout=0.5)
+    assert message_info.is_published() is True
+
+    delay()  # Only needed to let the coverage tracker fulfil its job.
+    mqtt_client.stop()
diff --git a/testing/test_integration.py b/testing/test_integration.py
new file mode 100644
index 0000000..87060be
--- /dev/null
+++ b/testing/test_integration.py
@@ -0,0 +1,101 @@
+import pytest
+
+from pytest_mqtt.model import MqttMessage
+
+
+def test_basic_submit_text_receive_binary(mosquitto, capmqtt):
+    """
+    Basic submit/receive roundtrip, with ASCII text payload (`str`).
+    Without further ado, the payloads will be received as `bytes`.
+    """
+    # Submit two MQTT messages.
+    capmqtt.publish(topic="foo", payload="bar")
+    capmqtt.publish(topic="baz", payload="qux")
+
+    # Demonstrate the `messages` property.
+    assert capmqtt.messages == [
+        MqttMessage(topic="foo", payload=b"bar", userdata=None),
+        MqttMessage(topic="baz", payload=b"qux", userdata=None),
+    ]
+
+    # Demonstrate the `records` property.
+    assert capmqtt.records == [
+        ("foo", b"bar", None),
+        ("baz", b"qux", None),
+    ]
+
+
+def test_basic_submit_and_receive_binary(mosquitto, capmqtt):
+    """
+    Basic submit/receive roundtrip, with binary payload (`bytes`).
+    """
+
+    # Submit two MQTT messages.
+    capmqtt.publish(topic="foo", payload=b"bar")
+    capmqtt.publish(topic="baz", payload=b"qux")
+
+    # Demonstrate the `messages` property.
+    assert capmqtt.messages == [
+        MqttMessage(topic="foo", payload=b"bar", userdata=None),
+        MqttMessage(topic="baz", payload=b"qux", userdata=None),
+    ]
+
+    # Demonstrate the `records` property.
+    assert capmqtt.records == [
+        ("foo", b"bar", None),
+        ("baz", b"qux", None),
+    ]
+
+
+@pytest.mark.capmqtt_decode_utf8
+def test_basic_submit_text_receive_text_marker(mosquitto, capmqtt):
+    """
+    Basic submit/receive roundtrip, with ASCII text payload (`str`).
+    By using the `capmqtt_decode_utf8` marker, the payloads will also be received
+    as `str`, after decoding them from `utf-8`.
+    """
+
+    # Submit two MQTT messages.
+    capmqtt.publish(topic="foo", payload="bar")
+    capmqtt.publish(topic="baz", payload="qux")
+
+    # Demonstrate the `messages` property.
+    assert capmqtt.messages == [
+        MqttMessage(topic="foo", payload="bar", userdata=None),
+        MqttMessage(topic="baz", payload="qux", userdata=None),
+    ]
+
+    # Demonstrate the `records` property.
+    assert capmqtt.records == [
+        ("foo", "bar", None),
+        ("baz", "qux", None),
+    ]
+
+
+@pytest.fixture
+def configure_capmqtt_decode_utf8(pytestconfig):
+    pytestconfig.option.capmqtt_decode_utf8 = True
+
+
+def test_basic_submit_text_receive_text_config(configure_capmqtt_decode_utf8, mosquitto, capmqtt):
+    """
+    Basic submit/receive roundtrip, with ASCII text payload (`str`).
+    By using the global `capmqtt_decode_utf8` config option, the payloads
+    will also be received as `str`, after decoding them from `utf-8`.
+    """
+
+    # Submit two MQTT messages.
+    capmqtt.publish(topic="foo", payload="bar")
+    capmqtt.publish(topic="baz", payload="qux")
+
+    # Demonstrate the `messages` property.
+    assert capmqtt.messages == [
+        MqttMessage(topic="foo", payload="bar", userdata=None),
+        MqttMessage(topic="baz", payload="qux", userdata=None),
+    ]
+
+    # Demonstrate the `records` property.
+    assert capmqtt.records == [
+        ("foo", "bar", None),
+        ("baz", "qux", None),
+    ]
diff --git a/testing/test_module_settings.py b/testing/test_module_settings.py
new file mode 100644
index 0000000..f6aa856
--- /dev/null
+++ b/testing/test_module_settings.py
@@ -0,0 +1,25 @@
+from pytest_mqtt.model import MqttMessage
+
+# Configure `capmqtt` to return `MqttMessage.payload` as `str`, decoded from `utf-8`.
+capmqtt_decode_utf8 = True
+
+
+def test_basic_submit_text_receive_text(mosquitto, capmqtt):
+    """
+    Basic submit/receive roundtrip, with ASCII text payload (`str`).
+    By using the module-wide `capmqtt_decode_utf8` setting, the payloads
+    will also be received as `str`, after decoding them from `utf-8`.
+    """
+
+    # Submit MQTT message.
+    capmqtt.publish(topic="foo", payload="bar")
+
+    # Demonstrate `messages` property.
+    assert capmqtt.messages == [
+        MqttMessage(topic="foo", payload="bar", userdata=None),
+    ]
+
+    # Demonstrate `records` property.
+    assert capmqtt.records == [
+        ("foo", "bar", None),
+    ]
diff --git a/testing/test_mosquitto.py b/testing/test_mosquitto.py
new file mode 100644
index 0000000..628a5cd
--- /dev/null
+++ b/testing/test_mosquitto.py
@@ -0,0 +1,27 @@
+import pytest
+
+from pytest_mqtt.util import delay
+from testing.util import DummyServer
+
+
+@pytest.fixture(scope="session")
+@pytest.mark.early
+def no_mqtt_broker(request):
+    server = DummyServer("localhost", 1883)
+    server.start()
+    delay()
+    request.addfinalizer(server.shutdown)
+    return server
+
+
+@pytest.fixture(scope="session")
+@pytest.mark.late
+def mosquitto_mqtt_broker(mosquitto):
+    return mosquitto
+
+
+@pytest.mark.skip(reason="Unable to run together with other test cases")
+@pytest.mark.run(order=1)
+def test_mosquitto_running(no_mqtt_broker, mosquitto_mqtt_broker):
+    assert mosquitto_mqtt_broker == ("localhost", 1883)
+    # no_mqtt_broker.shutdown()
diff --git a/testing/test_util.py b/testing/test_util.py
new file mode 100644
index 0000000..efda2fd
--- /dev/null
+++ b/testing/test_util.py
@@ -0,0 +1,9 @@
+from pytest_mqtt.util import probe_tcp_connect
+
+
+def test_probe_tcp_connect_available():
+    assert probe_tcp_connect("9.9.9.9", 443) is True
+
+
+def test_probe_tcp_connect_unavailable():
+    assert probe_tcp_connect("9.9.9.9", 444) is False
diff --git a/testing/util.py b/testing/util.py
new file mode 100644
index 0000000..573f681
--- /dev/null
+++ b/testing/util.py
@@ -0,0 +1,28 @@
+import socketserver
+import threading
+
+
+class DummyServer(threading.Thread):
+    class TcpServer(socketserver.TCPServer):
+        allow_reuse_address = True
+
+    class TCPHandler(socketserver.BaseRequestHandler):
+        def handle(self):
+            pass
+
+    def __init__(self, host, port):
+        super().__init__()
+        self.host = host
+        self.port = port
+        self.server = None
+
+    def run(self):
+        self.server = self.TcpServer((self.host, self.port), self.TCPHandler)
+        self.server.serve_forever(poll_interval=0.01)
+
+    def shutdown(self):
+        if self.server is not None:
+            # scdsc
+            # threading.Thread(target=self.server.shutdown).start()
+            self.server.shutdown()
+            self.join()