Run pytest in CI

.github/workflows/unittest.yml

@@ -0,0 +1,36 @@
+name: Unit Tests
+
+on: [push, pull_request]
+
+jobs:
+  pytest-win:
+    runs-on: windows-latest
+
+    steps:
+    - uses: actions/checkout@v3
+
+    - name: Install python libraries
+      shell: bash
+      run: |
+        pip install pytest -r tools/requirements.txt
+
+    - name: Run python unit tests (Windows)
+      shell: bash
+      run: |
+        pytest tools/isledecomp
+
+  pytest-ubuntu:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v3
+
+    - name: Install python libraries
+      shell: bash
+      run: |
+        pip install pytest -r tools/requirements.txt
+
+    - name: Run python unit tests (Ubuntu)
+      shell: bash
+      run: |
+        pytest tools/isledecomp

tools/isledecomp/tests/test_parser_statechange.py

@@ -1,3 +1,4 @@
+from typing import Optional
 import pytest
 from isledecomp.parser.parser import (
     ReaderState as _rs,
@@ -70,7 +71,7 @@
     "state, marker_type, new_state, expected_error", state_change_marker_cases
 )
 def test_state_change_by_marker(
-    state: _rs, marker_type: str, new_state: _rs, expected_error: None | _pe
+    state: _rs, marker_type: str, new_state: _rs, expected_error: Optional[_pe]
 ):
     p = DecompParser()
     p.state = state