try to fix flaky appveyor tests

conftest.py

@@ -3,7 +3,8 @@
 from os.path import abspath, dirname, join
 
 from tests.fixtures import (elasticapm_client, instrument, not_so_random,
-                            sending_elasticapm_client, validating_httpserver)
+                            sending_elasticapm_client, validating_httpserver,
+                            waiting_httpserver)
 from tests.utils.compat import middleware_setting
 
 try:

tests/fixtures.py

@@ -2,6 +2,8 @@
 import json
 import os
 import random
+import socket
+import time
 import zlib
 
 import jsonschema
@@ -94,10 +96,17 @@ def elasticapm_client(request):
     client.close()
 
 
+@pytest.fixture()
+def waiting_httpserver(httpserver):
+    wait_for_http_server(httpserver)
+    return httpserver
+
+
 @pytest.fixture()
 def validating_httpserver(request):
     server = ValidatingWSGIApp()
     server.start()
+    wait_for_http_server(server)
     request.addfinalizer(server.stop)
     return server
 
@@ -140,3 +149,15 @@ def instrument():
     elasticapm.instrument()
     yield
     elasticapm.uninstrument()
+
+
+def wait_for_http_server(httpserver, timeout=30):
+    start_time = time.time()
+    while True:
+        try:
+            sock = socket.create_connection(httpserver.server_address, timeout=0.1)
+            sock.close()
+            break
+        except socket.error:
+            if time.time() - start_time > timeout:
+                raise TimeoutError()

tests/instrumentation/urllib3_tests.py

@@ -6,10 +6,10 @@
 
 
 @mock.patch("elasticapm.traces.TransactionsStore.should_collect")
-def test_urllib3(should_collect, instrument, elasticapm_client, httpserver):
+def test_urllib3(should_collect, instrument, elasticapm_client, waiting_httpserver):
     should_collect.return_value = False
-    httpserver.serve_content('')
-    url = httpserver.url + '/hello_world'
+    waiting_httpserver.serve_content('')
+    url = waiting_httpserver.url + '/hello_world'
     parsed_url = urlparse.urlparse(url)
     elasticapm_client.begin_transaction("transaction")
     expected_sig = 'GET {0}'.format(parsed_url.netloc)