If you have the easy_install tool (otherwise see here) just type:
easy_install -U py
Now create a file test_sample.py with the following content:
You can now run the test file like this:
py.test test_sample.py
and will see output like this:
This output contains Python interpreter information, a list of test objects, a progress report and important details of the failure.
Where to go from here
features: overview and description of test features
plugins: a list of available plugins which each contain usage examples
tutorials: some blog entries and starting points with code examples
contact: if you want to feedback or have problems