Add more specs to cover subkeys scenarios

spec/features/profiles/gpg_keys_spec.rb

@@ -20,6 +20,18 @@ feature 'Profile > GPG Keys' do
       expect(page).to have_content('bette.cartwright@example.net Unverified')
       expect(page).to have_content(GpgHelpers::User2.fingerprint)
     end
+
+    scenario 'with multiple subkeys' do
+      fill_in('Key', with: GpgHelpers::User3.public_key)
+      click_button('Add key')
+
+      expect(page).to have_content('john.doe@example.com Unverified')
+      expect(page).to have_content(GpgHelpers::User3.fingerprint)
+
+      GpgHelpers::User3.subkey_fingerprints.each do |fingerprint|
+        expect(page).to have_content(fingerprint)
+      end
+    end
   end
 
   scenario 'User sees their key' do

spec/lib/gitlab/gpg/commit_spec.rb

@@ -63,6 +63,45 @@ describe Gitlab::Gpg::Commit do
           it_behaves_like 'returns the cached signature on second call'
         end
 
+        context 'commit signed with a subkey' do
+          let!(:commit) { create :commit, project: project, sha: commit_sha, committer_email: GpgHelpers::User3.emails.first }
+
+          let!(:user) { create(:user, email: GpgHelpers::User3.emails.first) }
+
+          let!(:gpg_key) do
+            create :gpg_key, key: GpgHelpers::User3.public_key, user: user
+          end
+
+          let(:gpg_key_subkey) do
+            gpg_key.subkeys.find_by(fingerprint: '0522DD29B98F167CD8421752E38FFCAF75ABD92A')
+          end
+
+          before do
+            allow(Rugged::Commit).to receive(:extract_signature)
+            .with(Rugged::Repository, commit_sha)
+            .and_return(
+              [
+                GpgHelpers::User3.signed_commit_signature,
+                GpgHelpers::User3.signed_commit_base_data
+              ]
+            )
+          end
+
+          it 'returns a valid signature' do
+            expect(described_class.new(commit).signature).to have_attributes(
+              commit_sha: commit_sha,
+              project: project,
+              gpg_key: gpg_key_subkey,
+              gpg_key_primary_keyid: gpg_key_subkey.keyid,
+              gpg_key_user_name: GpgHelpers::User3.names.first,
+              gpg_key_user_email: GpgHelpers::User3.emails.first,
+              verification_status: 'verified'
+            )
+          end
+
+          it_behaves_like 'returns the cached signature on second call'
+        end
+
         context 'user email does not match the committer email, but is the same user' do
           let!(:commit) { create :commit, project: project, sha: commit_sha, committer_email: GpgHelpers::User2.emails.first }
 

spec/models/gpg_signature_spec.rb

@@ -4,6 +4,7 @@ RSpec.describe GpgSignature do
   describe 'associations' do
     it { is_expected.to belong_to(:project) }
     it { is_expected.to belong_to(:gpg_key) }
+    it { is_expected.to belong_to(:gpg_key_subkey) }
   end
 
   describe 'validation' do