diff --git a/tool/test_for_warn_bundled_gems/README.md b/tool/test_for_warn_bundled_gems/README.md
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+This directory contains tests for the bundled gems warning under the Bundler.
+
+## Warning cases
+
+test_warn_bundled_gems.rb:
+test_warn_dependency.rb:
+test_warn_dash_gem.rb:
+  $ ruby test_warn_dash_gem.rb
+
+test_warn_bundle_exec.rb:
+  $ bundle exec ruby test_warn_bundle_exec.rb
+
+test_warn_bundle_exec_shebang.rb:
+  $ bundle exec ./test_warn_bundle_exec_shebang.rb
+
+## Not warning cases
+
+test_no_warn_dash_gem.rb:
+test_no_warn_bootsnap.rb:
+test_no_warn_dependency.rb:
+  $ ruby test_no_warn_dash_gem.rb