Add spec for COAR data migration

spec/migrations/migrate_code_owner_approval_status_to_protected_branches_in_batches_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+require Rails.root.join('db', 'post_migrate', '20190827102026_migrate_code_owner_approval_status_to_protected_branches_in_batches.rb')
+
+describe MigrateCodeOwnerApprovalStatusToProtectedBranchesInBatches, :migration do
+  let(:namespaces)         { table(:namespaces) }
+  let(:projects)           { table(:projects) }
+  let(:protected_branches) { table(:protected_branches) }
+
+  let(:namespace) do
+    namespaces.create!(
+      path: 'gitlab-instance-administrators',
+      name: 'GitLab Instance Administrators'
+    )
+  end
+
+  let(:project) do
+    projects.create!(
+      namespace_id: namespace.id,
+      name: 'GitLab Instance Administration'
+    )
+  end
+
+  let!(:protected_branch_1) do
+    protected_branches.create!(
+      name: "branch name",
+      project_id: project.id
+    )
+  end
+
+  describe '#up' do
+    context "when there's no projects needing approval" do
+      it "doesn't change any protected branch records" do
+        expect { migrate! }
+          .not_to change { ProtectedBranch.where(code_owner_approval_required: true).count }
+      end
+    end
+
+    context "when there's a project needing approval" do
+      let!(:project_needing_approval) do
+        projects.create!(
+          namespace_id: namespace.id,
+          name: 'GitLab Instance Administration',
+          merge_requests_require_code_owner_approval: true
+        )
+      end
+
+      let!(:protected_branch_2) do
+        protected_branches.create!(
+          name: "branch name",
+          project_id: project_needing_approval.id
+        )
+      end
+
+      it "changes N protected branch records" do
+        expect { migrate! }
+          .to change { ProtectedBranch.where(code_owner_approval_required: true).count }
+          .by(1)
+      end
+    end
+  end
+end