Any HTTP-based testing system can be used with WSGI applications.
Obviously any HTTP testing system can test any HTTP application.
However, some testing frameworks work more intimately with WSGI, and provide the ability the call WSGI applications in a controlled environment, with tracebacks and full use of debugging tools.
Intercepts normal Python calls to httplib, and redirects them to a WSGI application running in-process. Any testing tools written in Python can be made to test WSGI applications in-process.
See Testing WSGI Apps with twill for a description of the specifics on plugging these together. WSGI Intercept was originally written for Twill.
Extraction of paste.fixture.TestApp, rewriting portions to use WebOb.
Allows for testing WSGI applications without having to start a WSGI server.
Extensions to unittest for web frameworks.
Unit test your websites with code that acts like a web browser.
An easy to use programmatic web browser with special focus on testing. Used in Zope 3, but not Zope specific.