Summary

SERVER-126448 introduced storage-engine-agnostic test helpers enableWriteConflictForWrites
and enableWriteConflictForReads which deterministically inject a WriteConflictException
into a WiredTiger write (WT_OP_CHECK) or read/seek (WT_READ_CHECK). This ticket tracks
extending enableWriteConflictForWrites to other write-path subsystems that rely on
write-conflict retry/rollback but are pinned today only by slow integration/concurrency jstests.

Motivation

• Much WCE retry/safety behavior on the write path is covered only by jstests
  (profile_write_conflict.js, partial_unique_indexes.js, apply_ops_insert_write_conflict.js,
  collMod_writeconflict.js, reindex_writeconflict.js). Unit coverage would be faster,
  deterministic, and pin behavior at the source.

Candidate areas (non-index-build)

• Core CRUD writes – collection_write_path.cpp. collection_write_path_test.cpp already
  runs on real WiredTiger but injects no WCE. Add tests that fire a WCE during
  insertDocuments/updateDocument/deleteDocument/truncate/truncateRange and assert
  op-observer, pre-image, and index side effects roll back and a retry succeeds. With a secondary
  index present this also exercises wiredtiger_index.cpp WT_OP_CHECK.
• Fast-count / SizeStorer – WCE during wiredtiger_size_storer.cpp flush keeps record counts
  correct after rollback and a retry succeeds.
• Timeseries write path – WCE during timeseries_write_ops_internal.cpp reverts bucket-catalog
  state.

Caveats

• The fail point is process-global, so tests must arm it narrowly around the operation under test
  (see container_based_spiller_test.cpp for the pattern).