ONE in-memory stand-in for the suspension table, and the transaction primitives around it.

It replaces FakeFrontierRepo, and is much smaller than it was: seven query! clauses become four, and the ON CONFLICT merge — its trickiest and most bug-prone part, where two of the three real SQL bugs lived — is simply gone. Suspensions are append-only, so there is nothing to merge.

What this does NOT fix

It still pattern-matches SQL rather than executing it, so it cannot see a bug INSIDE the SQL. That is test/real_postgres_suspension_test.exs's job, and the reason that file exists: the first run of it caught a uuid-vs-text parameter mismatch that failed every insert, which this fake would have accepted happily.

Transactions are real here

transaction/2 and rollback/1 are implemented rather than absent, which matters more than it sounds. Suspension.transaction/1 only wraps when the repo exports transaction/2 — so a fake without it silently takes the no-transaction path, and a test asserting anything about transaction boundaries passes for the wrong reason.

Why this ships in lib/ rather than test/support/

Because it is for HOSTS, and Hex does not package test/support. A dependent that wanted it had to hand-copy the file — which is exactly what makes a copy drift, and one already did: the frontier's INSERT grew a column and the copies broke three releases later, in a repo whose own tests had passed the whole time.

Shipping it costs a module in the compiled artifact and removes a recurring failure mode for every dependent. It has no runtime callers and pulls in nothing.

Use

setup do
  start_supervised!(ReactiveDag.Test.FakeSuspensionRepo)
  ReactiveDag.Test.FakeSuspensionRepo.install()
end