RSpec and Database Transactions: Retry Logic Interoperability
26.5K reputation · 02 Aug 2024, 10:17 UTC
Transactional Isolation and Example Retries
Maintaining test isolation typically involves wrapping RSpec examples in database transactions using around(:each) hooks or integration tools like DatabaseCleaner. This ensures that writes are rolled back after each example to prevent state leakage.
When integrating external retry mechanisms—such as the rspec-retry gem—the execution flow between the retry loop and the transactional wrapper becomes critical. If a write operation occurs and the example fails, the behavior of the database state during the subsequent attempt depends on whether the transaction is rolled back before the retry is triggered.
In environments using non-transactional stores or specific commit behaviors, retrying an example that has already performed a write may lead to uniqueness constraint violations or duplicate records.
- Does the RSpec execution order guarantee that
aroundhooks are fully exited and rolled back before a retry attempt begins? - How can the state be consistently reset for non-transactional data stores when using example-level retries?
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26,525 reputation · 02 Aug 2024, 16:49 UTC
The transaction opened by use_transactional_fixtures (or DatabaseCleaner’s :transaction strategy) surrounds the entire example execution, not just the first attempt. When rspec-retry catches an exception and re‑runs the example, it does so inside the same open transaction because the around(:each) hook has not yet exited. Consequently, any writes that survived a savepoint rollback in the first attempt remain visible to the retry, which can cause duplicate‑key errors.
To obtain a clean slate between retries you must intervene before the retry starts. A reliable pattern is to use rspec-retry’s retry callback to manually roll back the outer transaction or to truncate/clean the database:
config.verbose_retry = true
config.retry_callback = proc do |exceptions|
# Reset state for the next attempt
if defined?(ActiveRecord)
ActiveRecord::Base.connection.rollback_transaction if ActiveRecord::Base.connection.transaction_open?
elsif defined?(DatabaseCleaner)
DatabaseCleaner.clean
end
end
After the callback runs, the next retry begins with a fresh transaction (or a clean truncation state), preventing the persistence of earlier writes. You can verify this by checking ActiveRecord::Base.connection.transaction_open? inside the retry callback; it should return false after the manual rollback.