Add xdist port handling (#248)

* add handling port number to run ios tests in parallel

* define PytestXdistWorker

* use gw0 if the number of worker is over the count of workers

Author: KazuCocoa

README.md

@@ -46,6 +46,23 @@ download and unarchive the source tarball (Appium-Python-Client-X.X.tar.gz).
 $ python -m autopep8 -r --global-config .config-pep8 -i .
 ```
 
+## Run tests
+
+```
+$ py.test test/functional/ios/find_by_ios_class_chain_tests.py
+```
+
+### In parallel for iOS
+1. Create simulators named 'iPhone 6s - 8100' and 'iPhone 6s - 8101'
+2. Install test libraries via pip
+    ```
+    $ pip install pytest pytest-xdist
+    ```
+3. Run tests
+    ```
+    $ py.test -n 2 test/functional/ios/find_by_ios_class_chain_tests.py
+    ```
+
 # Usage
 
 The Appium Python Client is fully compliant with the Selenium 3.0 specification

test/functional/ios/desired_capabilities.py

@@ -26,12 +26,45 @@ def PATH(p): return os.path.abspath(
 
 def get_desired_capabilities(app):
     desired_caps = {
-        'deviceName': 'iPhone 6s',
+        'deviceName': iphone_device_name(),
         'platformName': 'iOS',
         'platformVersion': '10.3',
         'app': PATH('../../apps/' + app),
         'automationName': 'XCUITest',
-        'allowTouchIdEnroll': True
+        'allowTouchIdEnroll': True,
+        'wdaLocalPort': wda_port(),
     }
 
     return desired_caps
+
+
+class PytestXdistWorker(object):
+    NUMBER = os.getenv('PYTEST_XDIST_WORKER')
+    COUNT = os.getenv('PYTEST_XDIST_WORKER_COUNT')  # Return 2 if `-n 2` is passed
+
+    @staticmethod
+    def gw(number):
+        if number >= PytestXdistWorker.COUNT:
+            return 'gw0'
+
+        return 'gw{}'.format(number)
+
+# If you run tests with pytest-xdist, you can run tests in parallel.
+
+
+def wda_port():
+    if PytestXdistWorker.NUMBER == PytestXdistWorker.gw(1):
+        return 8101
+
+    return 8100
+
+# Before running tests, you must have iOS simulators named 'iPhone 6s - 8100' and 'iPhone 6s - 8101'
+
+
+def iphone_device_name():
+    if PytestXdistWorker.NUMBER == PytestXdistWorker.gw(0):
+        return 'iPhone 6s - 8100'
+    elif PytestXdistWorker.NUMBER == PytestXdistWorker.gw(1):
+        return 'iPhone 6s - 8101'
+
+    return 'iPhone 6s'