Run pytest if tests are available

Author: tekktrik

.github/workflows/build.yml

@@ -24,5 +24,13 @@ jobs:
         submodules: true
     - name: Install pre-commit
       run: pip install pre-commit
+    - name: Install pytest
+      run: pip install pytest
     - name: Run pre-commit
       run: pre-commit run --all-files
+    - name: Install dependencies
+      run: |
+        pip install -r requirements.txt
+        pip install -r optional_requirements.txt
+    - name: Run pytest
+      run: if [[ -d tests ]]; then pytest; fi