1 files changed, 41 insertions, 0 deletions
diff --git a/spec/lib/gitlab/database/tables_sorted_by_foreign_keys_spec.rb b/spec/lib/gitlab/database/tables_sorted_by_foreign_keys_spec.rb
new file mode 100644
index 00000000000..97abd6d23bd
--- /dev/null
+++ b/spec/lib/gitlab/database/tables_sorted_by_foreign_keys_spec.rb
@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::Database::TablesSortedByForeignKeys do
+  let(:connection) { ApplicationRecord.connection }
+  let(:tables) { %w[_test_gitlab_main_items _test_gitlab_main_references] }
+
+  subject do
+    described_class.new(connection, tables).execute
+  end
+
+  before do
+    statement = <<~SQL
+      CREATE TABLE _test_gitlab_main_items (id serial NOT NULL PRIMARY KEY);
+
+      CREATE TABLE _test_gitlab_main_references (
+        id serial NOT NULL PRIMARY KEY,
+        item_id BIGINT NOT NULL,
+        CONSTRAINT fk_constrained_1 FOREIGN KEY(item_id) REFERENCES _test_gitlab_main_items(id)
+      );
+    SQL
+    connection.execute(statement)
+  end
+
+  describe '#execute' do
+    it 'returns the tables sorted by the foreign keys dependency' do
+      expect(subject).to eq([['_test_gitlab_main_references'], ['_test_gitlab_main_items']])
+    end
+
+    it 'returns both tables together if they are strongly connected' do
+      statement = <<~SQL
+        ALTER TABLE _test_gitlab_main_items ADD COLUMN reference_id BIGINT
+        REFERENCES _test_gitlab_main_references(id)
+      SQL
+      connection.execute(statement)
+
+      expect(subject).to eq([tables])
+    end
+  end
+end