chain sim - change slow-tests

.github/workflows/slow-tests.yml

@@ -1,15 +1,16 @@
 name: Tests
-
 on:
   push:
     branches:
       - master
   pull_request:
-
 jobs:
   test:
     name: Slow
     runs-on: ubuntu-latest
     steps:
+      - name: Check out code
+        uses: actions/checkout@v3
+
       - name: Slow tests
         run: make slow-tests