Add PyPy to the test matrix on Linux. Fixes #63.

Adds a 'dev' factor to the matrix as workaround for actions/setup-python#508.

Author: jaraco

.github/workflows/main.yml

@@ -7,20 +7,26 @@ jobs:
     strategy:
       matrix:
         python:
-        - 3.7
-        - '3.10'
-        - '3.11'
+        - "3.7"
+        - "3.10"
+        - "3.11"
+        # Workaround for actions/setup-python#508
+        dev:
+        - -dev
         platform:
         - ubuntu-latest
         - macos-latest
         - windows-latest
+        include:
+        - python: pypy3.9
+          platform: ubuntu-latest
     runs-on: ${{ matrix.platform }}
     steps:
       - uses: actions/checkout@v3
       - name: Setup Python
         uses: actions/setup-python@v4
         with:
-          python-version: ${{ matrix.python }}-dev
+          python-version: ${{ matrix.python }}${{ matrix.dev }}
       - name: Install tox
         run: |
           python -m pip install tox
@@ -52,7 +58,7 @@ jobs:
       - name: Setup Python
         uses: actions/setup-python@v4
         with:
-          python-version: "3.11-dev"
+          python-version: 3.11-dev
       - name: Install tox
         run: |
           python -m pip install tox