The way these tests work is similar to the existing field inferencing tests.
There is a .blend file that is opened and then we check the inferred structure
types from Python. A new `NodeSocket.inferred_structure_type` property is added
to be able to access this information. Other then the field inferencing tests,
this patch does not directly check the socket shapes, which are not always
exactly determined by the inferred structure type.
This also fixes a few issues I found while adding the tests.
Pull Request: https://projects.blender.org/blender/blender/pulls/140520
1bb49edf7f