There are tests for write conflicts between transactions (transactions_write_conflicts.js and transactions_write_conflicts_unique_indexes.js) but the tests for write conflicts between transaction and non-transaction (single document) writes are insuficient. Existing tests (write_conflicts_with_non_txns.js) only test insert-insert write conflicts missing on all other form of write conflicts:

• update-update
• upsert-upsert
• delete-delete
• update-delete
• delete-update

Testing those scenarios with non-transaction is particularly important given that in some of those operations Express Plan is used that is not covered with the existing test since it is not applied for insert operations.