Ensure user tests exist for a green check

Author: jdkula

.github/workflows/run-calculator-ci.yaml

@@ -48,4 +48,7 @@ jobs:
       - name: Run test
         run: |-
           cd calculator/tests
-          python3 your_tests.py
+          OUTPUT_RUNS=True python3 your_tests.py | tee ./output.txt \
+            && grep -q "TEST RUN:" ./output.txt \
+            && rm -f output.txt \
+          || echo "Either your tests failed or you didn't write any!"