Imported from eshu-hq/eshu (go/internal/reducer/factwrite/factwritetest/AGENTS.md). Install upstream with npx skills add eshu-hq/eshu --skill factwritetest. Copyright stays with the author.

Agent instructions: internal/reducer/factwrite/factwritetest

Scoped rules for this directory. The root AGENTS.md still applies.

What this package is

Test support for factwrite's batched-insert contract: a fake Execer (FakeExecer) and a decoder for the calls it records (DecodeBatchedFactCalls), importable from any reducer family's _test.go file (issue #6061). See README.md for the full purpose and usage.

Read first

• Repository-root AGENTS.md
• go/internal/reducer/AGENTS.md
• go/internal/reducer/factwrite/factwritetest/README.md
• go/internal/reducer/factwrite/README.md

Invariants

• This package is test support, not production code. Import it only from a _test.go file. It has no production call path and must not gain one.
• No import of the reducer root, ever, and no import of any family subpackage — only factwrite and the standard library.
• The 16-column decode order in DecodeBatchedFactCalls must track factwrite.ChunkArgs's column order exactly. It is a positional decode with no field-name binding; if factwrite.ChunkArgs adds, removes, or reorders a column, this package's decodeBatchedFactCall must change in the same commit or every caller's decoded rows silently misattribute values to the wrong field.
• The reducer root's own equivalent (reducer_fact_batch_insert_test_helpers_test.go, fakeWorkloadIdentityExecer/decodeBatchedFactCalls) is a SEPARATE, untouched copy, not a forwarder to this package and not deleted. Do not "consolidate" it into an alias without first confirming every one of its ~30 root callers compiles against the change — that migration was deliberately left out of scope for issue #6061's cicdrun split.

Common changes

Adding the versioned batched-insert decode (factwrite.BatchInsertVersionedQuery): mirror BatchedFactRow/DecodeBatchedFactCalls/decodeBatchedFactCall with the 17-column order the root's decodedBatchedVersionedFactRow/ decodeBatchedVersionedFactCalls already establish (reducer_fact_batch_insert_test_helpers_test.go), only when a family subpackage actually needs to assert on a versioned batched write — do not port it speculatively.

Failure modes to avoid

• Letting this package's column order drift from factwrite.ChunkArgs after a factwrite change.
• Deleting or aliasing the reducer root's own copy without migrating all ~30 of its current callers in the same change.
• Adding a production (non-test) import of this package anywhere.