Add unit tests for Gitaly types

spec/lib/gitlab/git/blob_spec.rb

@@ -276,6 +276,7 @@ describe Gitlab::Git::Blob, seed_helper: true do
         expect(blobs.count).to eq(1)
         expect(blobs).to all( be_a(Gitlab::Git::Blob) )
+        expect(blobs).to be_an(Array)
       end
       it 'accepts blob IDs as a lazy enumerator' do

spec/lib/gitlab/git/commit_spec.rb

@@ -102,6 +102,10 @@ describe Gitlab::Git::Commit, seed_helper: true do
         expect(described_class.find(repository, SeedRepo::Commit::ID)).to be_valid_commit
       end
+      it "returns an array of parent ids" do
+        expect(described_class.find(repository, SeedRepo::Commit::ID).parent_ids).to be_an(Array)
+      end
+
       it "should return valid commit for tag" do
         expect(described_class.find(repository, 'v1.0.0').id).to eq('6f6d7e7ed97bb5f0054f2b1df789b39ca89b6ff9')
       end