feat(client): add the dsh-client-test-runtime package

A jsdom slot test runtime for feature specs: a real Cordis Context, the
production SlotsService and web-react renderer, and typed session/workspace
doubles (TestSessions implements ISessions with FixtureSession sessions;
TestWorkspaces implements IWorkspaces), so the compiler flags fixture drift
when a production face changes. Fixtures feed plain data: list rows,
conversation snapshots, and ISession-typed behavior stubs; provide-bundle
materialization runs the shared SessionProvideChannel.

DOM snapshot support: declare()/renderSlot() mount a single slot inside a
data-slot wrapper for local .snap capture, and a snapshot serializer folds
CSS-module class hashes to their semantic locals and collapses svg internals
to a content fingerprint. The typed provide() constrains declared-service
fakes to Partial of the service's outward face.

packages/client/test-runtime/src/index.ts

@@ -0,0 +1,372 @@
+/**
+ * jsdom slot test runtime: a real small runtime — Cordis `Context`, the
+ * runtime `SlotsService`, and the web-react renderer — assembled around
+ * test-owned session/workspace doubles, so feature specs exercise
+ * declaration, registration, scope, store, inject, rendering, updates, and
+ * disposal without hand-building the machinery per suite.
+ *
+ * Not part of the product plugin graph (no `dshClient`); feature packages
+ * depend on it in devDependencies only. It copies no SlotCore/renderer/store
+ * machinery — everything mounts the production implementations.
+ * @module @deepseek-ai/dsh-client-test-runtime
+ */
+/* eslint-disable @typescript-eslint/no-redundant-type-constituents --
+ * `keyof SlotMap & string` is the declare-merge key pattern (see ui-slots):
+ * this compilation unit sees only the runtime's 'root' row, but consumer
+ * programs merge their own keys in; the rule fires on the narrow-map view. */
+import { Context, Inject } from 'cordis'
+import type { Fiber, Plugin } from 'cordis'
+import { createElement, Fragment, useSyncExternalStore } from 'react'
+import type { ReactNode } from 'react'
+import { act, render, within } from '@testing-library/react'
+import type { RenderResult } from '@testing-library/react'
+import type { queries } from '@testing-library/dom'
+import type { BoundFunctions } from '@testing-library/dom'
+import { SlotsService } from '@deepseek-ai/dsh-client-runtime/client'
+import { createSlotRenderer } from '@deepseek-ai/dsh-client-web-react'
+import type {
+  ChildrenDecl, ComposedProps, OwnerOf, SlotComponent, SlotMap, SlotRendererHost, StoreInstanceLike,
+} from '@deepseek-ai/dsh-client-ui-slots'
+import { registerDomSnapshotSerializer } from './snapshot.ts'
+import { TestSessions } from './sessions.ts'
+import { TestWorkspaces } from './workspaces.ts'
+import type { Stabilizer } from './fixtures.ts'
+
+export { domSnapshotSerializer, registerDomSnapshotSerializer } from './snapshot.ts'
+export { FixtureSession, TestSessions } from './sessions.ts'
+export { TestWorkspaces } from './workspaces.ts'
+export { conversationSnapshot, workspaceListState } from './fixtures.ts'
+export type { SessionBehaviorOverrides, SessionFixture, Stabilizer } from './fixtures.ts'
+
+/** Erased register face for the internal root call (the public declare seam holds the typing). */
+type ErasedRegister = (options: object, component: unknown) => () => void
+
+/**
+ * One rendered slot's local view, from {@link SlotTestRuntime.renderSlot}:
+ * the `data-slot` wrapper is the snapshot root (`expect(view.container)
+ * .toMatchSnapshot()` captures exactly this slot's output), Testing Library
+ * queries are bound inside it, and `update` re-renders with new owner props.
+ */
+export interface SlotView<K extends keyof SlotMap & string> {
+  /** The `<div data-slot="<key>">` wrapper around the slot's rendered output. */
+  readonly container: HTMLElement
+  /** Testing Library queries scoped to {@link SlotView.container}. */
+  readonly view: BoundFunctions<typeof queries>
+  /**
+   * Replace the owner props and flush the re-render (the render-site update:
+   * in production the owner recomputes the share and React re-renders).
+   * @param owner - the next owner props share.
+   */
+  update(owner: OwnerOf<K>): void
+}
+
+/**
+ * Mounted feature plugin handle: the live fiber plus an act-wrapped,
+ * idempotent dispose (unload cascade: entries, declared child slots, store
+ * instances, and provided services all fall together).
+ */
+export interface FeatureHandle {
+  /** The plugin's live Cordis fiber (state assertions, escape hatch). */
+  readonly fiber: Fiber
+  /**
+   * Dispose the plugin fiber inside React act; repeated calls no-op.
+   * @returns completion of the unload cascade.
+   */
+  dispose(): Promise<void>
+}
+
+/**
+ * Owner-props cell behind the auto frame: one external store the frame
+ * subscribes to, so {@link SlotTestRuntime.renderSlot} and
+ * {@link SlotView.update} drive React through the standard uSES seam.
+ */
+class OwnerPropsCell {
+  private readonly owners = new Map<string, object>()
+  private readonly listeners = new Set<() => void>()
+  private version = 0
+
+  /** Snapshot version for uSES pairing (bumped on every set). */
+  readonly getVersion = (): number => this.version
+
+  /**
+   * Subscribe to owner-props changes.
+   * @param fn - change callback.
+   * @returns unsubscribe.
+   */
+  readonly subscribe = (fn: () => void): (() => void) => {
+    this.listeners.add(fn)
+    return () => { this.listeners.delete(fn) }
+  }
+
+  /**
+   * Install or replace one key's owner props and notify (synchronous; the
+   * caller wraps in act).
+   * @param key - slot key.
+   * @param owner - owner props share.
+   */
+  set(key: string, owner: object): void {
+    this.owners.set(key, owner)
+    this.version += 1
+    for (const fn of [...this.listeners]) fn()
+  }
+
+  /** Keys with supplied owner props, in first-supply order. */
+  entries(): readonly (readonly [string, object])[] {
+    return [...this.owners.entries()]
+  }
+}
+
+/**
+ * The test-owned 'root' occupant: declares the child slots a suite needs
+ * through the REAL `slots.register`, with a caller-supplied minimal frame —
+ * the runtime never guesses a feature's page structure.
+ */
+export class TestRoot {
+  private disposeEntry: (() => void) | undefined
+
+  /**
+   * @param slots - the runtime SlotsService.
+   * @param stabilize - the owning runtime's act wrapper.
+   */
+  constructor(private readonly slots: SlotsService, private readonly stabilize: Stabilizer) {}
+
+  /**
+   * Register the root frame, declaring (and thereby claiming) the child
+   * slots. One declaration per runtime — a second call fails loud in the
+   * core ('root' is a single slot).
+   * @param children - child-slot declaration table (declaration + render authorization + runtime spec).
+   * @param frame - minimal frame component; its props derive from the declared keys (composed-props contract).
+   * @returns completion of the act-wrapped registration.
+   */
+  async declare<const D extends ChildrenDecl>(
+    children: D,
+    frame: SlotComponent<ComposedProps<'root', keyof NoInfer<D> & keyof SlotMap & string, undefined, object>>,
+  ): Promise<void> {
+    await this.stabilize(() => {
+      // Erased hop (same pattern as SlotsService's own implementation arm);
+      // the declare signature above is the typed seam.
+      this.disposeEntry = (this.slots.register as unknown as ErasedRegister)({ name: 'root', children }, frame)
+    })
+  }
+
+  /** Remove the root registration and collapse its declarations (runtime dispose path). */
+  release(): void {
+    this.disposeEntry?.()
+    this.disposeEntry = undefined
+  }
+}
+
+/**
+ * The assembled test runtime. Obtain via {@link SlotTestRuntime.create};
+ * dispose with {@link SlotTestRuntime.dispose} (afterEach). Public mutators
+ * are act-wrapped throughout — tests never handle SlotCore microtask
+ * batching or React act themselves.
+ */
+export class SlotTestRuntime {
+  /** The runtime's Cordis root (escape hatch: extra services via `ctx.provide`, raw `ctx.plugin` mounts). */
+  readonly ctx: Context
+  /** The production SlotsService mounted on {@link SlotTestRuntime.ctx}. */
+  readonly slots: SlotsService
+  /** The test-owned 'root' occupant. */
+  readonly root: TestRoot
+  /** Sessions double (list/current observable, cells, scopes, behavior faces). */
+  readonly sessions: TestSessions
+  /** Workspaces double (list observable, recorded intent actions). */
+  readonly workspaces: TestWorkspaces
+
+  private readonly stabilizer: Stabilizer = async (fn) => {
+    await act(async () => { await fn() })
+  }
+
+  private host: SlotRendererHost | undefined
+  private readonly views: RenderResult[] = []
+  private readonly handles: FeatureHandle[] = []
+  private disposed = false
+  /** Auto-frame state ({@link SlotTestRuntime.declare} / {@link SlotTestRuntime.renderSlot}). */
+  private readonly ownerCell = new OwnerPropsCell()
+  private readonly autoDeclared = new Set<string>()
+  private autoRootView: RenderResult | undefined
+
+  private constructor(ctx: Context, slots: SlotsService) {
+    this.ctx = ctx
+    this.slots = slots
+    this.root = new TestRoot(slots, this.stabilizer)
+    this.sessions = new TestSessions(this.stabilizer, ctx)
+    this.workspaces = new TestWorkspaces(this.stabilizer)
+    ctx.provide('sessions', this.sessions)
+    ctx.provide('workspaces', this.workspaces)
+    // Capturing install: the production renderer does the rendering; the
+    // wrapper only takes the host face for storeOf (no machinery copied).
+    const renderer = createSlotRenderer()
+    slots.install({
+      renderRoot: (host, ownerProps) => {
+        this.host = host
+        return renderer.renderRoot(host, ownerProps)
+      },
+    })
+  }
+
+  /**
+   * Assemble a runtime: real Context, mounted SlotsService, installed
+   * renderer, and the session/workspace doubles provided as services.
+   * @returns the ready runtime.
+   */
+  static async create(): Promise<SlotTestRuntime> {
+    registerDomSnapshotSerializer()
+    const ctx = new Context()
+    const fiber = ctx.plugin(SlotsService)
+    await fiber.await()
+    return new SlotTestRuntime(ctx, ctx.get('slots') as SlotsService)
+  }
+
+  /**
+   * Provide an extra service the feature under test injects (e.g. a layout
+   * fake). Sugar over `ctx.provide`, typed against the Context declaration
+   * merge: for a declared service name the fake must be a subset of that
+   * service's outward face (Partial — supply only what the feature calls),
+   * so a production face change breaks the fake at compile time. Undeclared
+   * names stay unchecked (ad-hoc test services).
+   * @param name - service name.
+   * @param value - service implementation (test double).
+   */
+  provide<K extends string>(name: K, value: K extends keyof Context ? Partial<Context[K]> : unknown): void {
+    this.ctx.provide(name, value)
+  }
+
+  /**
+   * Mount a feature plugin on a real fiber. Required services are prechecked
+   * so a missing provider fails loud instead of suspending the fiber forever
+   * (deliberate load-order suspension tests use `ctx.plugin` directly).
+   * @param plugin - plugin value (function, class, or `{ inject, apply }` object).
+   * @returns handle owning the fiber's explicit disposal.
+   */
+  async mount(plugin: Plugin): Promise<FeatureHandle> {
+    const required = Object.keys(Inject.resolve((plugin as { inject?: Inject }).inject))
+    const missing = required.filter(name => this.ctx.get(name) === undefined)
+    if (missing.length > 0) {
+      throw new Error(`mount would suspend: missing service(s) ${missing.join(', ')} — provide() them first`)
+    }
+    const fiber = this.ctx.plugin(plugin)
+    await this.stabilizer(async () => {
+      await fiber.await()
+    })
+    let disposed = false
+    const handle: FeatureHandle = {
+      fiber,
+      dispose: async () => {
+        if (disposed) return
+        disposed = true
+        await this.stabilizer(() => fiber.dispose())
+      },
+    }
+    this.handles.push(handle)
+    return handle
+  }
+
+  /**
+   * Render the root slot tree through the ctx-level entry (the shell's own
+   * seam): `ctx.slots.renderSlot('root', {})` under Testing Library.
+   * @returns the Testing Library view.
+   */
+  renderRoot(): RenderResult {
+    const view = render(createElement(Fragment, null, this.slots.renderSlot('root', {})))
+    this.views.push(view)
+    return view
+  }
+
+  /**
+   * Declare child slots under an auto-generated root frame — the single-slot
+   * mounting path for local DOM snapshots. Each key later supplied through
+   * {@link SlotTestRuntime.renderSlot} renders inside its own
+   * `<div data-slot="<key>">` wrapper (the snapshot root). Mutually exclusive
+   * with {@link TestRoot.declare} ('root' is a single slot); one call per
+   * runtime.
+   * @param children - child-slot declaration table (same contract as TestRoot.declare).
+   * @returns completion of the act-wrapped registration.
+   */
+  async declare(children: ChildrenDecl): Promise<void> {
+    for (const key of Object.keys(children)) this.autoDeclared.add(key)
+    const cell = this.ownerCell
+    const AutoFrame = (props: { renderSlot: (key: string, owner: object) => ReactNode }) => {
+      useSyncExternalStore(cell.subscribe, cell.getVersion)
+      return createElement(Fragment, null, cell.entries().map(([key, owner]) =>
+        createElement('div', { 'data-slot': key, key }, props.renderSlot(key, owner))))
+    }
+    await this.root.declare(children as never, AutoFrame as never)
+  }
+
+  /**
+   * Render one declared slot with its owner props and return the local view.
+   * The whole root tree mounts through the production assembly path
+   * (renderer, scope providers, store axis); only this key's output lands in
+   * the returned container. Call again with another key to view a sibling
+   * slot of the same tree.
+   * @param key - a key declared through {@link SlotTestRuntime.declare}.
+   * @param owner - owner props share for the render site.
+   * @returns the slot-local view (snapshot container, scoped queries, owner updates).
+   */
+  renderSlot<K extends keyof SlotMap & string>(key: K, owner: OwnerOf<K>): SlotView<K> {
+    if (!this.autoDeclared.has(key)) {
+      throw new Error(`renderSlot('${key}') without declare() — declare the key first (or use root.declare for a custom frame)`)
+    }
+    const install = (next: object): void => {
+      // Synchronous cell write inside act: the frame re-renders through uSES.
+      act(() => { 
+        this.ownerCell.set(key, next)
+      })
+    }
+    install(owner)
+    this.autoRootView ??= this.renderRoot()
+    const container = this.autoRootView.container.querySelector(`[data-slot="${key}"]`)
+    if (!(container instanceof HTMLElement)) {
+      throw new Error(`renderSlot('${key}'): the auto frame rendered no wrapper — was the runtime already disposed?`)
+    }
+    return { container, view: within(container), update: install }
+  }
+
+  /**
+   * Resolve the store instance the renderer would hand a slot's component
+   * (identity assertions, action-driven writes). Requires a prior
+   * {@link SlotTestRuntime.renderRoot} — the host face exists only inside the
+   * installed renderer, exactly as in production.
+   * @param key - slot key whose first entry declares the store.
+   * @param scopeKey - session id for session-scope slots; omit for root scope.
+   * @returns the live store instance.
+   */
+  storeOf(key: keyof SlotMap & string, scopeKey?: string): StoreInstanceLike {
+    if (this.host === undefined) {
+      throw new Error('storeOf before renderRoot() — the host face exists only inside the installed renderer')
+    }
+    const entry = this.host.entriesOf(key)[0]
+    if (entry === undefined) throw new Error(`storeOf('${key}'): no registration on the ledger`)
+    const instance = this.host.storeOf(entry, scopeKey)
+    if (instance === undefined) throw new Error(`storeOf('${key}'): the entry declares no store`)
+    return instance
+  }
+
+  /**
+   * Flush pending ledger/store notifications inside act — for mutations made
+   * outside the runtime's own methods (e.g. a direct `slots.register`).
+   * @returns completion of the act pass.
+   */
+  async flush(): Promise<void> {
+    await this.stabilizer(() => {})
+  }
+
+  /**
+   * Tear down: unmount React trees first, then dispose feature fibers, the
+   * root registration, minted session scopes, and persisted test state.
+   * Idempotent.
+   * @returns completion of the teardown.
+   */
+  async dispose(): Promise<void> {
+    if (this.disposed) return
+    this.disposed = true
+    this.autoRootView = undefined
+    for (const view of this.views.splice(0)) view.unmount()
+    for (const handle of this.handles.splice(0)) await handle.dispose()
+    this.root.release()
+    await this.sessions.disposeScopes()
+    localStorage.clear()
+  }
+}