1 files changed, 96 insertions, 0 deletions
diff --git a/spec/lib/gitlab/database/background_migration/batched_migration_spec.rb b/spec/lib/gitlab/database/background_migration/batched_migration_spec.rb
index 1ac9cbae036..31ae5e9b55d 100644
--- a/spec/lib/gitlab/database/background_migration/batched_migration_spec.rb
+++ b/spec/lib/gitlab/database/background_migration/batched_migration_spec.rb
@@ -211,6 +211,102 @@ RSpec.describe Gitlab::Database::BackgroundMigration::BatchedMigration, type: :m
         expect(active_migration).to eq(migration3)
       end
     end
+
+    context 'when there are no active migrations available' do
+      it 'returns nil' do
+        expect(active_migration).to eq(nil)
+      end
+    end
+  end
+
+  describe '.find_executable' do
+    let(:connection) { Gitlab::Database.database_base_models[:main].connection }
+    let(:migration_id) { migration.id }
+
+    subject(:executable_migration) { described_class.find_executable(migration_id, connection: connection) }
+
+    around do |example|
+      Gitlab::Database::SharedModel.using_connection(connection) do
+        example.run
+      end
+    end
+
+    context 'when the migration does not exist' do
+      let(:migration_id) { non_existing_record_id }
+
+      it 'returns nil' do
+        expect(executable_migration).to be_nil
+      end
+    end
+
+    context 'when the migration is not active' do
+      let!(:migration) { create(:batched_background_migration, :finished) }
+
+      it 'returns nil' do
+        expect(executable_migration).to be_nil
+      end
+    end
+
+    context 'when the migration is on hold' do
+      let!(:migration) { create(:batched_background_migration, :active, on_hold_until: 10.minutes.from_now) }
+
+      it 'returns nil' do
+        expect(executable_migration).to be_nil
+      end
+    end
+
+    context 'when the migration is not available for the current connection' do
+      let!(:migration) { create(:batched_background_migration, :active, gitlab_schema: :gitlab_not_existing) }
+
+      it 'returns nil' do
+        expect(executable_migration).to be_nil
+      end
+    end
+
+    context 'when ther migration exists and is executable' do
+      let!(:migration) { create(:batched_background_migration, :active, gitlab_schema: :gitlab_main) }
+
+      it 'returns the migration' do
+        expect(executable_migration).to eq(migration)
+      end
+    end
+  end
+
+  describe '.active_migrations_distinct_on_table' do
+    let(:connection) { Gitlab::Database.database_base_models[:main].connection }
+
+    around do |example|
+      Gitlab::Database::SharedModel.using_connection(connection) do
+        example.run
+      end
+    end
+
+    it 'returns one pending executable migration per table' do
+      # non-active migration
+      create(:batched_background_migration, :finished)
+      # migration put on hold
+      create(:batched_background_migration, :active, on_hold_until: 10.minutes.from_now)
+      # migration not availab for the current connection
+      create(:batched_background_migration, :active, gitlab_schema: :gitlab_not_existing)
+      # active migration that is no longer on hold
+      migration_1 = create(:batched_background_migration, :active, table_name: :users, on_hold_until: 10.minutes.ago)
+      # another active migration for the same table
+      create(:batched_background_migration, :active, table_name: :users)
+      # active migration for different table
+      migration_2 = create(:batched_background_migration, :active, table_name: :projects)
+      # active migration for third table
+      create(:batched_background_migration, :active, table_name: :namespaces)
+
+      actual = described_class.active_migrations_distinct_on_table(connection: connection, limit: 2)
+
+      expect(actual).to eq([migration_1, migration_2])
+    end
+
+    it 'returns epmty collection when there are no pending executable migrations' do
+      actual = described_class.active_migrations_distinct_on_table(connection: connection, limit: 2)
+
+      expect(actual).to be_empty
+    end
   end
 
   describe '.created_after' do