Test compiling docs in CI (#104)

.github/workflows/ci.yaml

@@ -9,6 +9,7 @@ on:
 env:
   # Increment this to invalidate the cache without modifying requirements.txt
   PIPCACHEVERSION: 0
+  PYTHONVERSION: '3.9.x'  # qutip does not support 3.10 yet
 
 jobs:
   pylint:
@@ -20,8 +21,7 @@ jobs:
         id: setup-python
         uses: actions/setup-python@v2
         with:
-          # qutip does not support 3.10 yet
-          python-version: '3.9.x'
+          python-version: ${{ env.PYTHONVERSION }}
       - name: Set up cache
         id: cache
         uses: actions/cache@v2
@@ -35,3 +35,36 @@ jobs:
         run: python -m pip install . pylint
       - name: Run pylint
         run: pylint --errors-only --jobs=0 pyEPR
+
+  test_docs:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out repo
+        uses: actions/checkout@v2
+      - name: Set up Python
+        id: setup-python
+        uses: actions/setup-python@v2
+        with:
+          python-version: ${{ env.PYTHONVERSION }}
+      - name: Set up cache
+        id: cache
+        uses: actions/cache@v2
+        with:
+          path: ~/.cache/pip
+          key: ${{ runner.os }}-${{ steps.setup-python.outputs.python-version }}-${{ hashFiles('requirements.txt') }}-${{ env.PIPCACHEVERSION }}
+          restore-keys: |
+            ${{ runner.os }}-${{ steps.setup-python.outputs.python-version }}-${{ hashFiles('requirements.txt') }}-
+            ${{ runner.os }}-${{ steps.setup-python.outputs.python-version }}-
+      - name: Install package and sphinx
+        run: python -m pip install . Sphinx
+      - name: Make docs
+        run: |
+          cd docs
+          make html
+      - name: Upload docs to artifact
+        uses: actions/upload-artifact@v2
+        if: always()
+        with:
+          name: docs
+          path: docs/build/html/
+          retention-days: 5