ci: another pass at getting OpenSCAD working

.github/workflows/ci.yml

@@ -50,7 +50,9 @@ jobs:
       run: openscad --info
       continue-on-error: true
 
-    - name: Run Unit Tests
+    - name: Run Unit Tests (Headless)
+      uses: coactions/setup-xvfb@6b00cf1889f4e1d5a48635647013c0508128ee1a
+      with:
         shell: bash
         working-directory: ./tests
         run: python3 -m unittest

tests/openscad_runner.py

@@ -117,7 +117,7 @@ class OpenScadRunner:
         #'--hardwarnings', # Does not work when setting variables by using functions
         #'--enable=fast-csg', # Requires Beta version of OpenSCAD
         #'--enable=predictible-output', # Requires Beta version of OpenSCAD
-        '--render=true'  # Required on headless systems
+        #'--render=true'  # Fully render geometry for images, instead of using fast preview mode.
         '--imgsize=1280,720',
         '--view=axes',
         '--projection=ortho',