---
type: knowledge
summary: Which suite answers which question, what a batch costs, and why two runs must never overlap
---

# What each suite judges

**The polyfill suite** exercises the published surface against the real broker: capabilities, reads, inboxes, reactivity. It is the one that judges whether the emulation behaves like the target.

**The applicative suite** drives the example application through a browser, as a person would — several identities, several pages, assertions on what is on screen rather than on what the library returns. It judges whether an application built on this package actually works, including the sign-in a person really performs.

**The reactivity suite** isolates document subscription.

A unit suite cannot replace any of them, and none of them replaces the unit suite: they are slow, they depend on live external services, and they cannot enumerate a case space.

## What a batch costs, and why

Every `batch` mints its own physical user by driving the wallet application's real interface, then discards the previous one. That is deliberate — identities must not leak between runs — and it puts a floor under every run that no test filter can remove.

Consequences worth knowing before optimizing anything: the setup runs before any `journey`, so a filter saves journey time only; and the wallet profile is a single directory shared by every suite.

## Two runs must never overlap

Because the profile is shared and each `batch` discards what it finds, a second run started while a first is alive destroys the first — which then fails in a way that reads as a product defect. Several measurements were lost to this before it was made structural.

It is now enforced by a lock rather than by discipline, and a browser left behind by a killed run is reclaimed. If you ever find yourself reasoning about "was another run going?", check the lock rather than your memory.

The related trap that made it self-perpetuating: discarding the profile was once conditioned on a marker written at the *end* of a batch, so a run killed before writing it left a profile the next run happily reused — and inherited its breakage. Discarding now keys on the profile itself.