don't check rate if no tests executed

.github/workflows/ci.yml

@@ -329,8 +329,12 @@ jobs:
       - name: Check test coverage for PR
         if: ${{ matrix.mutation == 'true' && github.event.pull_request }}
         run: |
-          # check if executed have at most 50% survival rate
-          cr-rate --estimate --confidence 99.9 --fail-over 50 session-vs-master.sqlite
+          # only check if we have executed tests (if no code changes, the
+          # cr-rate will fail)
+          if ! $( cr-report session-vs-master.sqlite | tail -n 3 | grep -q 'complete.*100.00%' ); then
+            # check if executed have at most 50% survival rate
+            cr-rate --estimate --confidence 99.9 --fail-over 50 session-vs-master.sqlite
+          fi
       - name: instrumental test coverage on PR
         if: ${{ contains(matrix.opt-deps, 'instrumental') && github.event.pull_request }}
         env:
@@ -417,7 +421,8 @@ jobs:
           key: sessions-${{ github.sha }}
       - name: Install cosmic-ray
         run: |
-          pip3 install https://github.com/sixty-north/cosmic-ray/archive/master.zip
+          #pip3 install https://github.com/sixty-north/cosmic-ray/archive/master.zip
+          pip3 install https://github.com/tomato42/cosmic-ray/archive/no-executed.zip
           pip install pytest-timeout
       - name: Install dependencies
         run: |