Add integration tests for TurboGears 2

Make sure we don't break TurboGears by testing a minimal app using
Kajiki renderer.

pyproject.toml

@@ -64,6 +64,11 @@ include = [
     "/tests",
 ]
 
+[tool.hatch.envs.hatch-test]
+extra-dependencies = [
+    "TurboGears2 @ git+https://github.com/TurboGears/tg2.git@942335e4de87d36ec7dc480b1e0e41dc01e6f0ff",
+]
+
 [[tool.hatch.envs.hatch-test.matrix]]
 python = ["3.9", "3.10", "3.11", "3.12"]
 

tests/integration/test_tg2.py

@@ -0,0 +1,91 @@
+"""Test we don't break TurboGears' usage of our Python API."""
+
+import dataclasses
+import wsgiref.util
+from pathlib import Path
+from typing import Any
+
+import pytest
+
+from kajiki import i18n
+
+DATA = Path(__file__).resolve().parent.parent / "data"
+GOLDEN = DATA / "golden"
+
+
+@pytest.fixture
+def tg2():
+    """Import tg2 (if available), and cleanup its mess."""
+    orig_gettext = i18n.gettext
+    try:
+        import tg
+    except ImportError:
+        pytest.skip("TurboGears not installed")
+    else:
+        yield tg
+    finally:
+        i18n.gettext = orig_gettext
+
+
+@pytest.fixture
+def tg2_app(tg2):
+    """Create a new tg2 app with defaults for testing.
+
+    Returns:
+        A WSGI application.
+    """
+
+    class RootController(tg2.TGController):
+        @tg2.expose("kajiki_test_data.kitchensink")
+        def index(self):
+            return {}
+
+    config = tg2.MinimalApplicationConfigurator()
+    config.update_blueprint(
+        {
+            "root_controller": RootController(),
+            "renderers": ["kajiki"],
+            "templating.kajiki.template_extension": ".html",
+        }
+    )
+    return config.make_wsgi_app()
+
+
+@dataclasses.dataclass
+class Response:
+    """Encapsulates a response for testing."""
+
+    status: str
+    headers: list[tuple[str, str]]
+    body: str
+
+
+def app_request(app: Any, path: str = "/", method: str = "GET") -> Response:
+    response_status = ""
+    response_headers = []
+
+    def start_response(status, headers):
+        nonlocal response_status
+        nonlocal response_headers
+        response_status = status
+        response_headers = headers
+
+    environ = {}
+    wsgiref.util.setup_testing_defaults(environ)
+    environ["REQUEST_METHOD"] = method
+    environ["PATH_INFO"] = path
+
+    response_body = b"".join(app(environ, start_response))
+
+    return Response(
+        status=response_status,
+        headers=response_headers,
+        body=response_body,
+    )
+
+
+def test_smoke_tg2(tg2_app):
+    """Do a basic smoke test of using kajiki renderer on tg2."""
+    response = app_request(tg2_app, "/")
+    assert response.status == "200 OK"
+    assert response.body == (GOLDEN / "kitchensink1.html").read_bytes()