Summary

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

Motivation

• The read/restore path is effectively untested at the unit level for write conflicts
• Much WCE retry/safety behavior is covered only by jstests (profile_write_conflict.js,
  write_conflict_preserves_plan_stats.js, agg_cursor_invalidations.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 assertop-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.
• Read / cursor restore – extend enableWriteConflictForReads coverage to RecordStore andSortedDataInterface cursor restore() across capped, oplog, clustered, and index cursors (only one standard record-store cursor case exists today).
• Fast-count / SizeStorer – WCE during wiredtiger_size_storer.cpp flush keeps record
• Timeseries write path – WCE during timeseries_write_ops_internal.cpp reverts bucket-catalog
  state.

Cleanup

• Migrate collection_cache_recoverer_test.cpp (test CacheRecovererBubblesUpCachePressureErrors)
  from the hardcoded FailPointEnableBlock{"WTWriteConflictExceptionForReads"} to
  enableWriteConflictForReads for engine-agnostic consistency. This is the only remaining hardcoded WT write-conflict fail-point name in unit tests; the TODO SERVER-126415 markers from the original change have already been resolved.

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).
• Some query-execution stages run on mock storage and cannot use these helpers; those remain integration tests.