Avoiding debugging issues¶

When you set a breakpoint, e.g. via import pdb;pdb.set_trace() and run a collection of tests, you may receive the following message:

Can't use pdb.set_trace when running a layer as a subprocess!

This happens when you are running a collection of tests which span multiple layers, and a previous layer could not be safely torn down in-process, so the testrunner had to spawn a subprocess instead.

The workaround is to run just the one test you are trying to debug.

You can read more about this issue in zope.testrunner’s documentation.