Fix pytest setup() deprecation in tests (#492)

* Fix pytest setup() deprecation in tests

* Replace setup() with setup_method() in func tests

* Fix issues in arbor tests, wrt to sorted dir content etc

* Make compatible with python 3.12

* Add python 3.12 to default tests

Author: wvangeit

.github/workflows/test.yml

@@ -12,7 +12,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        python-version: ["3.8", "3.9", "3.10", "3.11"]
+        python-version: ["3.8", "3.9", "3.10", "3.11", "3.12"]
         include:
           - os: macos-latest
             python-version: "3.10"