Removes factories on Cluster background migration

'Populate cluster kubernetes namespace' was using factories for their
specs. According to our documentation (see spec/migrations/readme.md),
we should use table helper to create a temproary ActiveRecord::Base
derived model for a table.

spec/lib/gitlab/background_migration/populate_cluster_kubernetes_namespace_table_spec.rb

@@ -2,92 +2,88 @@
 
 require 'spec_helper'
 
-# rubocop:disable RSpec/FactoriesInMigrationSpecs
 describe Gitlab::BackgroundMigration::PopulateClusterKubernetesNamespaceTable, :migration, schema: 20181022173835 do
+  include MigrationHelpers::ClusterHelpers
+
   let(:migration) { described_class.new }
-  let(:clusters) { create_list(:cluster, 10, :project, :provided_by_gcp) }
+  let(:clusters_table) { table(:clusters) }
+  let(:cluster_projects_table) { table(:cluster_projects) }
+  let(:cluster_kubernetes_namespaces_table) { table(:clusters_kubernetes_namespaces) }
+  let(:projects_table) { table(:projects) }
+  let(:namespaces_table) { table(:namespaces) }
+  let(:provider_gcp_table) { table(:cluster_providers_gcp) }
+  let(:platform_kubernetes_table) { table(:cluster_platforms_kubernetes) }
 
   before do
-    clusters
+    create_cluster_project_list(10)
   end
 
   shared_examples 'consistent kubernetes namespace attributes' do
     it 'should populate namespace and service account information' do
-      subject
+      migration.perform
 
       clusters_with_namespace.each do |cluster|
-        project = cluster.project
-        cluster_project = cluster.cluster_projects.first
+        cluster_project = cluster_projects_table.find_by(cluster_id: cluster.id)
+        project = projects_table.find(cluster_project.project_id)
+        kubernetes_namespace = cluster_kubernetes_namespaces_table.find_by(cluster_id: cluster.id)
         namespace = "#{project.path}-#{project.id}"
-        kubernetes_namespace = cluster.reload.kubernetes_namespace
 
         expect(kubernetes_namespace).to be_present
-        expect(kubernetes_namespace.cluster_project).to eq(cluster_project)
-        expect(kubernetes_namespace.project).to eq(cluster_project.project)
-        expect(kubernetes_namespace.cluster).to eq(cluster_project.cluster)
+        expect(kubernetes_namespace.cluster_project_id).to eq(cluster_project.id)
+        expect(kubernetes_namespace.project_id).to eq(cluster_project.project_id)
+        expect(kubernetes_namespace.cluster_id).to eq(cluster_project.cluster_id)
         expect(kubernetes_namespace.namespace).to eq(namespace)
         expect(kubernetes_namespace.service_account_name).to eq("#{namespace}-service-account")
       end
     end
   end
 
-  subject { migration.perform }
-
   context 'when no Clusters::Project has a Clusters::KubernetesNamespace' do
-    let(:cluster_projects) { Clusters::Project.all }
+    let(:cluster_projects) { cluster_projects_table.all }
 
     it 'should create a Clusters::KubernetesNamespace per Clusters::Project' do
       expect do
-        subject
-      end.to change(Clusters::KubernetesNamespace, :count).by(cluster_projects.count)
+        migration.perform
+      end.to change(Clusters::KubernetesNamespace, :count).by(cluster_projects_table.count)
     end
 
     it_behaves_like 'consistent kubernetes namespace attributes' do
-      let(:clusters_with_namespace) { clusters }
+      let(:clusters_with_namespace) { clusters_table.all }
     end
   end
 
   context 'when every Clusters::Project has Clusters::KubernetesNamespace' do
     before do
-      clusters.each do |cluster|
-        create(:cluster_kubernetes_namespace,
-               cluster_project: cluster.cluster_projects.first,
-               cluster: cluster,
-               project: cluster.project)
-      end
+      create_kubernetes_namespace(clusters_table.all)
     end
 
     it 'should not create any Clusters::KubernetesNamespace' do
       expect do
-        subject
+        migration.perform
       end.not_to change(Clusters::KubernetesNamespace, :count)
     end
   end
 
   context 'when only some Clusters::Project have Clusters::KubernetesNamespace related' do
-    let(:with_kubernetes_namespace) { clusters.first(6) }
-    let(:with_no_kubernetes_namespace) { clusters.last(4) }
+    let(:with_kubernetes_namespace) { clusters_table.first(6) }
+    let(:with_no_kubernetes_namespace) { clusters_table.last(4) }
 
     before do
-      with_kubernetes_namespace.each do |cluster|
-        create(:cluster_kubernetes_namespace,
-               cluster_project: cluster.cluster_projects.first,
-               cluster: cluster,
-               project: cluster.project)
-      end
+      create_kubernetes_namespace(with_kubernetes_namespace)
     end
 
     it 'creates limited number of Clusters::KubernetesNamespace' do
       expect do
-        subject
+        migration.perform
       end.to change(Clusters::KubernetesNamespace, :count).by(with_no_kubernetes_namespace.count)
     end
 
     it 'should not modify clusters with Clusters::KubernetesNamespace' do
-      subject
+      migration.perform
 
       with_kubernetes_namespace.each do |cluster|
-        expect(cluster.kubernetes_namespaces.count).to eq(1)
+        kubernetes_namespace = cluster_kubernetes_namespaces_table.where(cluster_id: cluster.id)
+        expect(kubernetes_namespace.count).to eq(1)
       end
     end
 
@@ -96,4 +92,3 @@ describe Gitlab::BackgroundMigration::PopulateClusterKubernetesNamespaceTable, :
     end
   end
 end
-# rubocop:enable RSpec/FactoriesInMigrationSpecs

spec/support/migrations_helpers/cluster_helpers.rb

+# frozen_string_literal: true
+
+module MigrationHelpers
+  module ClusterHelpers
+    # Creates a list of cluster projects.
+    def create_cluster_project_list(quantity)
+      group = namespaces_table.create(name: 'gitlab-org', path: 'gitlab-org')
+
+      quantity.times do |id|
+        create_cluster_project(group, id)
+      end
+    end
+
+    # Creates dependencies for a cluster project:
+    # - Group
+    # - Project
+    # - Cluster
+    # - Project - cluster relationship
+    # - GCP provider
+    # - Platform Kubernetes
+    def create_cluster_project(group, id)
+      project = projects_table.create!(
+        name: "project-#{id}",
+        path: "project-#{id}",
+        namespace_id: group.id
+      )
+
+      cluster = clusters_table.create(
+        name: 'test-cluster',
+        cluster_type: 3,
+        provider_type: :gcp,
+        platform_type: :kubernetes
+      )
+
+      cluster_projects_table.create(project_id: project.id, cluster_id: cluster.id)
+
+      provider_gcp_table.create!(
+        gcp_project_id: "test-gcp-project-#{id}",
+        endpoint: '111.111.111.111',
+        cluster_id: cluster.id,
+        status: 3,
+        num_nodes: 1,
+        zone: 'us-central1-a'
+      )
+
+      platform_kubernetes_table.create(
+        cluster_id: cluster.id,
+        api_url: 'https://kubernetes.example.com',
+        encrypted_token: 'a' * 40,
+        encrypted_token_iv: 'a' * 40
+      )
+    end
+
+    # Creates a Kubernetes namespace for a list of clusters
+    def create_kubernetes_namespace(clusters)
+      clusters.each do |cluster|
+        cluster_project = cluster_projects_table.find_by(cluster_id: cluster.id)
+        project = projects_table.find(cluster_project.project_id)
+        namespace = "#{project.path}-#{project.id}"
+
+        cluster_kubernetes_namespaces_table.create(
+          cluster_project_id: cluster_project.id,
+          cluster_id: cluster.id,
+          project_id: cluster_project.project_id,
+          namespace: namespace,
+          service_account_name: "#{namespace}-service-account"
+        )
+      end
+    end
+  end
+end