Test with pytest-xdist

.travis.yml

@@ -1,20 +1,20 @@
 language: python
 matrix:
   include:
-    - python: 3.5
-      env: TOX_ENV=py35
-    - python: 3.6
-      env: TOX_ENV=py36
     - python: 3.7
       env: TOX_ENV=py37
       # TODO: the dist and sudo keys are currently needed to use Python 3.7.
       # They should be removed once Travis-CI supports 3.7 on the default image.
       dist: xenial
       sudo: true
+python:
+  - 3.5
+  - 3.6
+cache: pip
 
 install: pip install tox-travis coveralls
 
-script: tox -e $TOX_ENV
+script: tox
 
 after_success:
   - tox -e coverage-report

setup.py

@@ -1,3 +1,4 @@
+# coding=utf-8
 import re
 from pathlib import Path
 

tox.ini

@@ -4,7 +4,8 @@ minversion = 2.5.0
 
 [testenv]
 extras = testing
-commands = coverage run -m pytest {posargs}
+deps = pytest-xdist
+commands = coverage run -m pytest -n auto {posargs}
 
 [testenv:coverage-report]
 deps = coverage