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...