RailsDatabaseCleaner đảm bảo mỗi test bắt đầu với DB sạch — tránh test state rò rỉ sang test khác.
Ba strategy chính:
| Strategy | Cơ chế | Tốc độ | Dùng khi |
|---|---|---|---|
transaction | Wrap test trong transaction, rollback sau | Nhanh nhất | Unit/request test không cần JS |
truncation | TRUNCATE tất cả bảng | Chậm | System test (Capybara + JS), cần data persist |
deletion | DELETE FROM từng bảng | Trung bình | Ít dùng |
ruby
# spec/support/database_cleaner.rb
RSpec.configure do |config|
config.before(:suite) { DatabaseCleaner.strategy = :transaction }
config.around(:each) { |ex| DatabaseCleaner.cleaning { ex.run } }
# System tests cần truncation vì Capybara dùng thread riêng
config.before(:each, type: :system) { DatabaseCleaner.strategy = :truncation }
endRSpec transactional fixtures (use_transactional_fixtures: true) cũng làm được điều tương tự nhưng DatabaseCleaner linh hoạt hơn khi mix nhiều loại test.
DatabaseCleaner ensures each test starts with a clean DB state — preventing test state from leaking between examples.
Three main strategies:
| Strategy | Mechanism | Speed | Use when |
|---|---|---|---|
transaction | Wraps test in a transaction, rolls back after | Fastest | Unit/request tests without JS |
truncation | TRUNCATEs all tables | Slowest | System tests (Capybara + JS), when data must persist |
deletion | DELETE FROM each table | Medium | Rarely used |
ruby
# spec/support/database_cleaner.rb
RSpec.configure do |config|
config.before(:suite) { DatabaseCleaner.strategy = :transaction }
config.around(:each) { |ex| DatabaseCleaner.cleaning { ex.run } }
# System tests need truncation — Capybara uses a separate thread
config.before(:each, type: :system) { DatabaseCleaner.strategy = :truncation }
endRSpec transactional fixtures (use_transactional_fixtures: true) achieves the same thing but DatabaseCleaner is more flexible when mixing test types.