Add test infrastructure and bump to v2026.3.1

Test infrastructure:
- Add .devcontainer/devcontainer.json for Linux-based dev environment
- Add requirements_test.txt with pytest-homeassistant-custom-component
- Add pyproject.toml with asyncio_mode=auto for pytest
- 30 config_flow tests: parsing, schemas, flow steps, options flow, validation
- 8 hub tests: gateway creation, PGN filters, callbacks, status handling
- 10 sensor tests: init, state, availability, TTL, update frequency
- 70% overall code coverage (config_flow 92%, const 100%, sensor 71%)

Version bump:
- Update manifest.json to nmea2000==2026.3.1 and version 2026.3.1

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: tomer-w

.devcontainer/devcontainer.json

@@ -0,0 +1,26 @@
+{
+    "name": "ha-nmea2000",
+    "image": "mcr.microsoft.com/devcontainers/python:3.13",
+    "postCreateCommand": "pip install --upgrade pip && pip install -r requirements.txt && pip install -r requirements_test.txt",
+    "customizations": {
+        "vscode": {
+            "extensions": [
+                "charliermarsh.ruff",
+                "ms-python.python",
+                "ms-python.vscode-pylance",
+                "ryanluker.vscode-coverage-gutters"
+            ],
+            "settings": {
+                "files.eol": "\n",
+                "editor.tabSize": 4,
+                "editor.formatOnSave": true,
+                "[python]": {
+                    "editor.defaultFormatter": "charliermarsh.ruff"
+                },
+                "python.testing.pytestEnabled": true,
+                "python.testing.pytestArgs": ["tests"]
+            }
+        }
+    },
+    "remoteUser": "vscode"
+}

custom_components/nmea2000/manifest.json

@@ -11,7 +11,7 @@
   "iot_class": "local_push",
   "issue_tracker": "https://github.com/tomer-w/ha-nmea2000/issues",
   "requirements": [
-    "nmea2000==2026.3.0"
+    "nmea2000==2026.3.1"
   ],
-  "version": "2026.3.0"
+  "version": "2026.3.1"
 }

pyproject.toml

@@ -0,0 +1,2 @@
+[tool.pytest.ini_options]
+asyncio_mode = "auto"

requirements_test.txt

@@ -0,0 +1,3 @@
+pytest
+pytest-asyncio
+pytest-homeassistant-custom-component

tests/__init__.py

@@ -0,0 +1,21 @@
+"""Fixtures for ha-nmea2000 tests."""
+import pytest
+from unittest.mock import patch
+
+pytest_plugins = ["pytest_homeassistant_custom_component"]
+
+
+@pytest.fixture(autouse=True)
+def auto_enable_custom_integrations(enable_custom_integrations):
+    """Enable loading custom integrations in all tests."""
+    yield
+
+
+@pytest.fixture(autouse=True)
+def bypass_setup_entry():
+    """Prevent async_setup_entry from running during config flow tests."""
+    with patch(
+        "custom_components.nmea2000.async_setup_entry", return_value=True
+    ):
+        yield
+