Explicit app factory test.

tests/test_app_factory.py

@@ -0,0 +1,24 @@
+import flask
+import flask_babel as babel
+
+
+def test_app_factory():
+    b = babel.Babel()
+
+    def locale_selector():
+        return 'de_DE'
+
+    def create_app():
+        app_ = flask.Flask(__name__)
+        b.init_app(
+            app_,
+            default_locale='en_US',
+            locale_selector=locale_selector
+        )
+        return app_
+
+    app = create_app()
+    with app.test_request_context():
+        assert str(babel.get_locale()) == 'de_DE'
+        assert babel.gettext(u'Hello %(name)s!', name='Peter') == \
+               'Hallo Peter!'