1 files changed, 20 insertions, 0 deletions
diff --git a/spec/ruby/core/kernel/require_spec.rb b/spec/ruby/core/kernel/require_spec.rb
index dc3da4b7e6..4029e68725 100644
--- a/spec/ruby/core/kernel/require_spec.rb
+++ b/spec/ruby/core/kernel/require_spec.rb
@@ -16,6 +16,26 @@ describe "Kernel#require" do
     Kernel.should have_private_instance_method(:require)
   end
 
+  provided = %w[complex enumerator rational thread ruby2_keywords]
+  ruby_version_is "3.1" do
+    provided << "fiber"
+  end
+
+  it "#{provided.join(', ')} are already required" do
+    out = ruby_exe("puts $LOADED_FEATURES", options: '--disable-gems --disable-did-you-mean')
+    features = out.lines.map { |line| File.basename(line.chomp, '.*') }
+
+    # Ignore CRuby internals
+    features -= %w[encdb transdb windows_1252 windows_31j]
+    features.reject! { |feature| feature.end_with?('-fake') }
+
+    features.sort.should == provided.sort
+
+    code = provided.map { |f| "puts require #{f.inspect}\n" }.join
+    required = ruby_exe(code, options: '--disable-gems')
+    required.should == "false\n" * provided.size
+  end
+
   it_behaves_like :kernel_require_basic, :require, CodeLoadingSpecs::Method.new
   it_behaves_like :kernel_require, :require, CodeLoadingSpecs::Method.new
 end