CI: add macOS and Winwdows tests via Github Actions

Adds tests for macOS and Windows with the dummy converter. Tests won't
actually perform the conversion. But it should be enough for us to test
the remainder of the codebase.

Fixes #229

.github/workflows/ci.yml

@@ -0,0 +1,34 @@
+name: Tests
+on:
+  push:
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  windows:
+    runs-on: windows-latest
+    env:
+      DUMMY_CONVERSION: True
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
+        with:
+          python-version: '3.10'
+      - run: pip install poetry
+      - run: poetry install
+      - name: Run CLI tests
+        run: poetry run make test
+
+  macOS:
+    runs-on: macos-latest
+    env:
+      DUMMY_CONVERSION: True
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
+        with:
+          python-version: '3.10'
+      - run: pip install poetry
+      - run: poetry install
+      - name: Run CLI tests
+        run: poetry run make test

tests/__init__.py

@@ -1,4 +1,3 @@
-import os
 import sys
 from pathlib import Path
 

tests/test_cli.py

@@ -126,6 +126,9 @@ class TestCli(TestBase):
             # to tokenize it.
             args = (args,)
 
+        if os.environ.get("DUMMY_CONVERSION", False):
+            args = ("--unsafe-dummy-conversion", *args)
+
         # TODO: Replace this with `contextlib.chdir()` [1], which was added in
         # Python 3.11.
         #