docker-compose.yml in handsome_fencer-crypto-0.1.8 vs docker-compose.yml in handsome_fencer-crypto-0.1.9

@@ -5,7 +5,12 @@
   ruby_gem:
     build:
       context: .
       dockerfile: roro/containers/ruby_image/Dockerfile
     environment:
-      - RUBY_IMAGE=${RUBY_IMAGE}
+      - RUBY_VERSION=${RUBY_VERSION}
     command: bundle exec rake test
+    volumes:
+      - gem_cache:/gems
+
+volumes:
+  gem_cache:
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