Added a scenario to test installing a gem.

test/ruby/install_gem.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+
+set -e
+
+# Optional: Import test library
+source dev-container-features-test-lib
+
+check "gem installed" bash -c "gem install rubocop"
+
+# Report result
+reportResults

test/ruby/scenarios.json

@@ -8,6 +8,15 @@
             }
         }
     },
+    "install_gem": {
+        "image": "mcr.microsoft.com/devcontainers/base:bullseye",
+        "remoteUser": "vscode",
+        "features": {
+            "ruby": {
+                "version": "latest"
+            }
+        }
+    },
     "additional_versions": {
         "image": "mcr.microsoft.com/devcontainers/base:bullseye",
         "features": {