diff --git a/.travis.yml b/.travis.yml
index fbcaaa0..e284a81 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,7 +2,6 @@ sudo: false
 language: python
 python:
   - 2.7
-  - 3.3
   - 3.4
   - 3.5
   - 3.6
diff --git a/requirements/dev.pip b/requirements/dev.pip
index c7f0076..d3c430d 100644
--- a/requirements/dev.pip
+++ b/requirements/dev.pip
@@ -5,20 +5,16 @@
 
 -r exe.pip
 
+docopt  # For `/bin/bumpver.py`.
+gevent>=1.1b4; python_version >= '3'
+mock; python_version <= '3.2'
 pip>=7
+passlib>=1.6
+pytest>=2.3; python_version != '3.3'
+pytest>=2.3,<3.3; python_version == '3.3'
 setuptools
 setuptools-git>=0.3
-passlib>=1.6
 tox
-wheel>=0.25.0
-pytest>=2.3;        python_version != '3.3'
-pytest>=2.3,<3.3;   python_version == '3.3'
-webtest;        python_version != '2.5'
-mock;           python_version <= '3.2'
-gevent>=1.1b4;  python_version >= '3'
 twine>=1.7
-
-WebOb==0.9.6.1;         python_version == '2.5'
-BeautifulSoup==3.2.1;   python_version == '2.5'
-WebTest==1.4.3;         python_version == '2.5'
-docopt                  # For `/bin/bumpver.py`.
\ No newline at end of file
+webtest; python_version != '2.5'
+wheel>=0.25.0
diff --git a/tox.ini b/tox.ini
index c60c9e8..f0bdb7f 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,10 +1,24 @@
 [tox]
-envlist = py27,py33,py34,py35
+envlist = py27,py34,py35,py36,pypy,pypy3
 
 [testenv]
 deps=-r{toxinidir}/requirements/dev.pip
-commands=py.test []
+whitelist_externals=
+    /bin/sh
+commands=
+    /bin/sh -c "{env:PYPISERVER_SETUP_CMD:true}"
+    pytest []
 sitepackages=False
 
 [pytest]
 norecursedirs = bin parts develop-eggs eggs venv .* _* CVS {args}
+
+[testenv:pre_twine]
+# Allow calling ``tox -e pre_twine`` to test pypiserver with the most
+# recent prerelease of twine.
+whitelist_externals=
+    tox
+setenv=
+    PYPISERVER_SETUP_CMD=pip install --upgrade --pre --index-url https://test.pypi.org/simple/ --extra-index-url https://pypi.org/simple twine
+commands=
+    tox