[rubygems/rubygems] test Bundler::Fetcher that error raised when attempting load unexpected class

https://github.com/rubygems/rubygems/commit/795e796a9e

spec/bundler/bundler/fetcher_spec.rb

@@ -159,4 +159,34 @@ RSpec.describe Bundler::Fetcher do
       end
     end
   end
+
+  describe "#fetch_spec" do
+    let(:name) { 'name' }
+    let(:version) { '1.3.17' }
+    let(:platform) { 'platform' }
+    let(:downloader) { double("downloader")}
+    let(:body) { double(Net::HTTP::Get, body: downloaded_data)}
+
+    context "when attempting to load a Gem::Specification" do
+      let(:spec) { Gem::Specification.new(name, version) }
+      let(:downloaded_data) { Zlib::Deflate.deflate(Marshal.dump(spec)) }
+
+      it "returns the spec" do
+        expect(Bundler::Fetcher::Downloader).to receive(:new).and_return(downloader)
+        expect(downloader).to receive(:fetch).once.and_return(body)
+        result = fetcher.fetch_spec([name, version, platform])
+        expect(result).to eq(spec)
+      end
+    end
+    
+    context "when attempting to load an unexpected class" do
+      let(:downloaded_data) { Zlib::Deflate.deflate(Marshal.dump(3)) }
+      
+      it "raises a HTTPError error" do
+        expect(Bundler::Fetcher::Downloader).to receive(:new).and_return(downloader)
+        expect(downloader).to receive(:fetch).once.and_return(body)
+        expect { fetcher.fetch_spec([name, version, platform]) }.to raise_error(Bundler::HTTPError, /Gemspec .* contained invalid data/i)
+      end
+    end
+  end
 end