test: make state promise work on different types

This will be used for awaiting state on a Stream as well as a Model.

src/Model.discontinuity.test.ts

@@ -5,7 +5,7 @@ import { it, describe, expect, vi, beforeEach } from 'vitest';
 
 import Model from './Model.js';
 import { ModelOptions } from './types/model.js';
-import { getEventPromises, modelStatePromise } from './utilities/test/promises.js';
+import { getEventPromises, statePromise } from './utilities/test/promises.js';
 
 vi.mock('ably/promises');
 
@@ -65,10 +65,10 @@ describe('Model', () => {
     await subscriptionCalls[0];
     expect(subscriptionSpy).toHaveBeenNthCalledWith(1, null, '0');
 
-    await modelStatePromise(model, 'ready');
+    await statePromise(model, 'ready');
 
     suspendChannel();
-    await modelStatePromise(model, 'ready');
+    await statePromise(model, 'ready');
 
     await subscriptionCalls[1];
     expect(subscriptionSpy).toHaveBeenNthCalledWith(2, null, '1');

src/Model.test.ts

@@ -9,7 +9,7 @@ import { IStreamFactory } from './StreamFactory.js';
 import type { ModelState, ModelStateChange, ModelOptions, Event } from './types/model.d.ts';
 import type { MutationMethods, EventComparator, MutationContext } from './types/mutations.d.ts';
 import { createMessage, customMessage } from './utilities/test/messages.js';
-import { getNthEventPromise, getEventPromises, modelStatePromise, timeout } from './utilities/test/promises.js';
+import { getNthEventPromise, getEventPromises, statePromise, timeout } from './utilities/test/promises.js';
 
 vi.mock('ably/promises');
 
@@ -99,10 +99,10 @@ describe('Model', () => {
       logger,
     });
     const ready = model.$register({ $sync: sync });
-    await modelStatePromise(model, 'preparing');
+    await statePromise(model, 'preparing');
     completeSync();
     await ready;
-    await modelStatePromise(model, 'ready');
+    await statePromise(model, 'ready');
     expect(sync).toHaveBeenCalledOnce();
     expect(model.optimistic).toEqual(simpleTestData);
     expect(model.confirmed).toEqual(simpleTestData);
@@ -960,7 +960,7 @@ describe('Model', () => {
 
     // The 3rd event throws when applying the update, which should
     // trigger a resync and get the latest counter value.
-    const preparingPromise = modelStatePromise(model, 'preparing');
+    const preparingPromise = statePromise(model, 'preparing');
     events.channelEvents.next(customMessage('id_3', 'testEvent', String(++counter)));
     const { reason } = (await preparingPromise) as ModelStateChange;
     expect(reason).to.toBeDefined();

src/utilities/test/promises.ts

@@ -1,8 +1,6 @@
 import { Subject, lastValueFrom, take } from 'rxjs';
 
-import type Model from '../../Model.js';
-import type { ModelState } from '../../types/model.js';
-import type { MutationMethods } from '../../types/mutations.js';
+import { EventListener } from '../EventEmitter.js';
 
 export const getNthEventPromise = <T>(subject: Subject<T>, n: number) => lastValueFrom(subject.pipe(take(n)));
 
@@ -14,7 +12,12 @@ export const getEventPromises = <T>(subject: Subject<T>, n: number) => {
   return promises;
 };
 
-export const modelStatePromise = <T, M extends MutationMethods>(model: Model<T, M>, state: ModelState) =>
-  new Promise((resolve) => model.whenState(state, model.state, resolve));
+interface StateListener<T, S> {
+  state: S;
+  whenState(targetState: S, currentState: S, listener: EventListener<T>, ...listenerArgs: unknown[]);
+}
+
+export const statePromise = <T, S>(object: StateListener<T, S>, state: S) =>
+  new Promise((resolve) => object.whenState(state, object.state, resolve));
 
 export const timeout = (ms: number = 0) => new Promise((resolve) => setTimeout(resolve, ms));