Yes, your description sounds right, and I had zero-ed in on the same park of the mock code when I was doing my investigation.

I know that this is a peculiar situation, but one thing to note is that `inspect.signature` gets the signature right on these wrapped methods. You can see this if you were to add in an appropriate spot the following code to the script:

====
from inspect import signature

print(signature(a.with_arg))  # prints `(x)`
print(signature(a.no_arg))    # prints `()`
====

Is there a reason why mock calculates the signature on its own rather than relying on `inspect`?