add test and changelog for SERVER_NAME app.run default

ref #2152

CHANGES

@@ -17,6 +17,8 @@ Bugfix release, unreleased
   within the imported application module.
 - Fix encoding behavior of ``app.config.from_pyfile`` for Python 3. Fix
   ``#2118``.
+- Use the``SERVER_NAME`` config if it is present as default values for
+  ``app.run``. ``#2109``, ``#2152``
 
 Version 0.12
 ------------

tests/test_basic.py

@@ -1681,3 +1681,20 @@ def test_run_server_port(monkeypatch):
     hostname, port = 'localhost', 8000
     app.run(hostname, port, debug=True)
     assert rv['result'] == 'running on %s:%s ...' % (hostname, port)
+
+
+@pytest.mark.parametrize('host,port,expect_host,expect_port', (
+    (None, None, 'pocoo.org', 8080),
+    ('localhost', None, 'localhost', 8080),
+    (None, 80, 'pocoo.org', 80),
+    ('localhost', 80, 'localhost', 80),
+))
+def test_run_from_config(monkeypatch, host, port, expect_host, expect_port):
+    def run_simple_mock(hostname, port, *args, **kwargs):
+        assert hostname == expect_host
+        assert port == expect_port
+
+    monkeypatch.setattr(werkzeug.serving, 'run_simple', run_simple_mock)
+    app = flask.Flask(__name__)
+    app.config['SERVER_NAME'] = 'pocoo.org:8080'
+    app.run(host, port)