Once you have changed the test runner to pytest, you can take advantage of writing plain assert statements instead of self.assert* methods.

Converting all the method calls is boring and error-prone, that's why the unittest2pytest tool exists. It converts all self.assert* method calls to plain asserts, and also converts self.assertRaises calls to the appropriate pytest idiom.

Install it using pip:

λ pip install unittest2pytest

Once installed, you can now execute it on the files you want:

λ unittest2pytest test_simple2.py
RefactoringTool: Refactored test_simple2.py
--- test_simple2.py (original)
+++ test_simple2.py (refactored)
@@ -5,6 +5,7 @@
 import unittest
 from collections import namedtuple
 from pathlib import Path
+import pytest

 DATA = """
 Main Grid,48,44
@@ -49,12 +50,12 @@
         self.grids = list(iter_grids_from_csv...