test(slug): test 'slug_ref' function

.github/actions/bats/Dockerfile

@@ -0,0 +1,5 @@
+FROM dduportal/bats:latest
+
+COPY entrypoint.sh /entrypoint.sh
+
+ENTRYPOINT ["/entrypoint.sh"]

.github/actions/bats/entrypoint.sh

@@ -0,0 +1,3 @@
+#!/usr/bin/env sh
+
+/sbin/bats ./

.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
+