add nightly tests against pre-releases

.github/workflows/nightly.yml

@@ -0,0 +1,22 @@
+name: Nightly
+
+on:
+  schedule:
+    - cron: '0 2 * * *' # run at 2 AM UTC
+
+jobs:
+  test-against-pre-releases-of-dependencies:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v1
+    - name: Set up Python
+      uses: actions/setup-python@v2
+      with:
+        python-version: 3.8
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        pip install tox tox-gh-actions
+    - name: Test with tox
+      run: tox -e pre-release

setup.cfg

@@ -81,3 +81,14 @@ commands =
     autoflake --recursive --in-place --remove-duplicate-keys --remove-unused-variables .
     isort .
     black .
+
+
+[testenv:pre-release]  # test against pre-releases of dependencies
+pip_pre = true
+deps = pytest
+       hypothesis
+       scipy
+basepython = python3.8
+commands = pytest --hypothesis-profile ci \
+           {posargs}
+extras =