Also collect coverage data
MODIFY
dev-requirements.txt
dev-requirements.txt
@@ -9,4 +9,5 @@ tornado==4.2.1
PySocks==1.5.6
pkginfo>=1.0,!=1.3.0
psutil==4.3.1
+pytest-cov==2.5.1
pytest==3.1.0

MODIFY
tox.ini
tox.ini
@@ -5,7 +5,7 @@ envlist = flake8-py3, py26, py27, py33, py34, py35, py36, pypy
deps= -r{toxinidir}/dev-requirements.txt
commands=
pip install .[socks,secure]
- py.test test
+ py.test --cov urllib3 test
setenv =
PYTHONWARNINGS=always::DeprecationWarning
passenv = CFLAGS LDFLAGS TRAVIS APPVEYOR CRYPTOGRAPHY_OSX_NO_LINK_FLAGS

Also collect coverage data