Add a basic interoperability test for Jinja2 extraction

tests/interop/jinja2_data/hello.html

@@ -0,0 +1 @@
+{% trans %}Hello, {{ name }}!{% endtrans %}

tests/interop/jinja2_data/mapping.cfg

@@ -0,0 +1 @@
+[jinja2: *.html]

tests/interop/test_jinja2_interop.py

@@ -0,0 +1,20 @@
+import pathlib
+
+import pytest
+
+from babel.messages import frontend
+
+jinja2 = pytest.importorskip("jinja2")
+
+jinja2_data_path = pathlib.Path(__file__).parent / "jinja2_data"
+
+
+def test_jinja2_interop(monkeypatch, tmp_path):
+    """
+    Test that babel can extract messages from Jinja2 templates.
+    """
+    monkeypatch.chdir(jinja2_data_path)
+    cli = frontend.CommandLineInterface()
+    pot_file = tmp_path / "messages.pot"
+    cli.run(['pybabel', 'extract', '--mapping', 'mapping.cfg', '-o', str(pot_file), '.'])
+    assert '"Hello, %(name)s!"' in pot_file.read_text()

tox.ini

@@ -5,6 +5,7 @@ envlist =
     pypy3
     py{38}-pytz
     py{311,312}-setuptools
+    py312-jinja
 
 [testenv]
 extras =
@@ -15,6 +16,7 @@ deps =
     tzdata;sys_platform == 'win32'
     pytz: pytz
     setuptools: setuptools
+    jinja: jinja2>=3.0
 allowlist_externals = make
 commands = make clean-cldr test
 setenv =