feat(network): Add network context manager (#367)

This PR adds a `Network` helper class that allows to create networks and
connect containers programmatically.

The networks are context-managed resources like containers created via
`DockerContainer`.

Please also see tests for a usage example :)

---------

Co-authored-by: Kevin Wittek <kiview@users.noreply.github.com>
Co-authored-by: Max Pfeiffer <max@maxpfeiffer.ch>
Co-authored-by: Jakob Beckmann <32326425+f4z3r@users.noreply.github.com>
Co-authored-by: David Ankin <daveankin@gmail.com>
Co-authored-by: Carli* Freudenberg <carli.freudenberg@energymeteo.de>
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Vemund Santi <vemund@santi.no>

core/testcontainers/core/container.py

@@ -10,6 +10,7 @@
 from testcontainers.core.docker_client import DockerClient
 from testcontainers.core.exceptions import ContainerStartException
 from testcontainers.core.labels import LABEL_SESSION_ID, SESSION_ID
+from testcontainers.core.network import Network
 from testcontainers.core.utils import inside_container, is_arm, setup_logger
 from testcontainers.core.waiting_utils import wait_container_is_ready, wait_for_logs
 
@@ -46,6 +47,8 @@ def __init__(
         self._container = None
         self._command = None
         self._name = None
+        self._network: Optional[Network] = None
+        self._network_aliases: Optional[list[str]] = None
         self._kwargs = kwargs
 
     def with_env(self, key: str, value: str) -> Self:
@@ -61,6 +64,14 @@ def with_exposed_ports(self, *ports: int) -> Self:
             self.ports[port] = None
         return self
 
+    def with_network(self, network: Network) -> Self:
+        self._network = network
+        return self
+
+    def with_network_aliases(self, *aliases) -> Self:
+        self._network_aliases = aliases
+        return self
+
     def with_kwargs(self, **kwargs) -> Self:
         self._kwargs = kwargs
         return self
@@ -87,6 +98,8 @@ def start(self) -> Self:
             **self._kwargs,
         )
         logger.info("Container started: %s", self._container.short_id)
+        if self._network:
+            self._network.connect(self._container.id, self._network_aliases)
         return self
 
     def stop(self, force=True, delete_volume=True) -> None:

core/testcontainers/core/network.py

@@ -0,0 +1,41 @@
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+import uuid
+from typing import Optional
+
+from testcontainers.core.docker_client import DockerClient
+
+
+class Network:
+    """
+    Network context manager for programmatically connecting containers.
+    """
+
+    def __init__(self, docker_client_kw: Optional[dict] = None, docker_network_kw: Optional[dict] = None) -> None:
+        self.name = str(uuid.uuid4())
+        self._docker = DockerClient(**(docker_client_kw or {}))
+        self._docker_network_kw = docker_network_kw or {}
+
+    def connect(self, container_id: str, network_aliases: Optional[list] = None):
+        self._network.connect(container_id, aliases=network_aliases)
+
+    def remove(self) -> None:
+        self._network.remove()
+
+    def __enter__(self) -> "Network":
+        self._network = self._docker.client.networks.create(self.name, **self._docker_network_kw)
+        self.id = self._network.id
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb) -> None:
+        self.remove()

core/tests/test_network.py

@@ -0,0 +1,43 @@
+from testcontainers.core.container import DockerContainer
+from testcontainers.core.docker_client import DockerClient
+from testcontainers.core.network import Network
+
+NGINX_ALPINE_SLIM_IMAGE = "nginx:1.25.4-alpine-slim"
+
+
+def test_network_gets_created_and_cleaned_up():
+    with Network() as network:
+        docker = DockerClient()
+        networks_list = docker.client.networks.list(network.name)
+        assert networks_list[0].name == network.name
+        assert networks_list[0].id == network.id
+    assert not docker.client.networks.list(network.name)
+
+
+def test_containers_can_communicate_over_network():
+    with Network() as network:
+        with (
+            DockerContainer(NGINX_ALPINE_SLIM_IMAGE)
+            .with_name("alpine1")
+            .with_network_aliases("alpine1-alias-1", "alpine1-alias-2")
+            .with_network(network) as alpine1
+        ):
+            with (
+                DockerContainer(NGINX_ALPINE_SLIM_IMAGE)
+                .with_name("alpine2")
+                .with_network_aliases("alpine2-alias-1", "alpine2-alias-2")
+                .with_network(network) as alpine2
+            ):
+                assert_can_ping(alpine1, "alpine2")
+                assert_can_ping(alpine1, "alpine2-alias-1")
+                assert_can_ping(alpine1, "alpine2-alias-2")
+
+                assert_can_ping(alpine2, "alpine1")
+                assert_can_ping(alpine2, "alpine1-alias-1")
+                assert_can_ping(alpine2, "alpine1-alias-2")
+
+
+def assert_can_ping(container: DockerContainer, remote_name: str):
+    status, output = container.exec("ping -c 1 %s" % remote_name)
+    assert status == 0
+    assert "64 bytes" in str(output)