Add CI cache

.drone.yml

@@ -14,19 +14,12 @@ trigger:
     - push
 
 steps:
-  - name: compute cache key
-    image: docker.io/library/elixir:1.18.3-otp-27
-    commands:
-      - echo "$DRONE_REPO_OWNER/$DRONE_REPO_NAME/" >> .cache_key
-
   - name: restore-cache
     image: drillster/drone-volume-cache
     settings:
       restore: true
       mount:
         - ./deps
-        - ./_build
-      ttl: 30
     volumes:
       - name: cache
         path: /tmp/cache
@@ -78,9 +71,7 @@ steps:
       # Fetch dependencies
       - mix deps.get
       # Run tests
-      # - mix test
-      # TODO: remove this, added only for testing
-      - mix compile
+      - mix test
 
   - name: rebuild-cache
     image: drillster/drone-volume-cache