test(slug): test 'slug_ref' function

.github/workflows/ci.yml

@@ -0,0 +1,17 @@
+name: ci
+
+on: [push, pull_request]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+
+      - name: Check out code
+        uses: actions/checkout@v1
+
+      - name: Tests
+        uses: ./.github/actions/bats
+