Actions: Test pypy-3.7 and pypy-3.8

.github/workflows/test.yml

@@ -6,7 +6,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
-        python-version: [3.6, 3.7, 3.8, 3.9, pypy3]
+        python-version: [3.6, 3.7, 3.8, 3.9, pypy-3.7, pypy-3.8]
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v2