updates CI

Author: saxix

.github/workflows/tests.yml

@@ -50,7 +50,7 @@ jobs:
 
       - name: Run test suite
         run: |
-          COV_CMD=$(if [ ${{ matrix.env }} == 3.12 ]; then echo "--cov=pytest_echo --cov-report=xml"; else echo ; fi)
+          export COV_CMD=$(if [ ${{ matrix.env }} == 3.12 ]; then echo "--cov=pytest_echo --cov-report=xml"; else echo ; fi)
           tox run --skip-pkg-install -e ${{ matrix.env }} $COV_CMD
         env:
           PYTEST_ADDOPTS: "-vv --durations=20"