Expand CI (#291)

* Test against CPython 3.8 and 3.9

* Test against PyPy 2 and 3

* Add macOS to CI

* Add 291.misc.rst

* Switch to CPython 3.8 for checks

* Comment on use of second-most-recent minor release for checks

.github/workflows/ci.yml

@@ -8,11 +8,16 @@ on:
 
 jobs:
   test:
-    name: ${{ matrix.task.name}} - ${{ matrix.python.name }}
-    runs-on: ubuntu-latest
+    name: ${{ matrix.task.name}} - ${{ matrix.os.name }} ${{ matrix.python.name }}
+    runs-on: ${{ matrix.os.runs-on }}
     strategy:
       fail-fast: false
       matrix:
+        os:
+          - name: Linux
+            runs-on: ubuntu-latest
+          - name: macOS
+            runs-on: macos-latest
         python:
           - name: CPython 2.7
             tox: py27
@@ -26,6 +31,18 @@ jobs:
           - name: CPython 3.7
             tox: py37
             action: 3.7
+          - name: CPython 3.8
+            tox: py38
+            action: 3.8
+          - name: CPython 3.9
+            tox: py39
+            action: 3.9
+          - name: PyPy 2
+            tox: pypy2
+            action: pypy2
+          - name: PyPy 3
+            tox: pypy3
+            action: pypy3
         task:
           - name: Test
             tox: tests
@@ -48,7 +65,7 @@ jobs:
 
     - name: Codecov
       run: |
-        codecov -n "GitHub Actions - ${{ matrix.task.name}} - ${{ matrix.python.name }}"
+        codecov -n "GitHub Actions - ${{ matrix.task.name}} - ${{ matrix.os.name }} ${{ matrix.python.name }}"
 
   check:
     name: ${{ matrix.task.name}} - ${{ matrix.python.name }}
@@ -57,9 +74,11 @@ jobs:
       fail-fast: false
       matrix:
         python:
-          - name: CPython 3.6
-            tox: py36
-            action: 3.6
+          # Using second most recent minor release for whatever little
+          # increase in stability over using the latest minor.
+          - name: CPython 3.8
+            tox: py38
+            action: 3.8
         task:
           - name: Flake8
             tox: flake8