Allow sanic test client to bind to a random port (#1376)

tests/test_test_client_port.py

@@ -0,0 +1,34 @@
+import socket
+
+from sanic.testing import PORT, SanicTestClient
+from sanic.response import json, text
+
+# ------------------------------------------------------------ #
+#  UTF-8
+# ------------------------------------------------------------ #
+
+
+def test_test_client_port_none(app):
+    @app.get('/get')
+    def handler(request):
+        return text('OK')
+
+    test_client = SanicTestClient(app, port=None)
+
+    request, response = test_client.get('/get')
+    assert response.text == 'OK'
+
+    request, response = test_client.post('/get')
+    assert response.status == 405
+
+
+def test_test_client_port_default(app):
+    @app.get('/get')
+    def handler(request):
+        return json(request.transport.get_extra_info('sockname')[1])
+
+    test_client = SanicTestClient(app)
+    assert test_client.port == PORT
+
+    request, response = test_client.get('/get')
+    assert response.json == PORT