feat(util-dev): add createStubObservable util

hoist from wallet TipTracker tests

Author: mkazlauskas

packages/util-dev/src/createStubObservable.ts

@@ -0,0 +1,13 @@
+import { Observable } from 'rxjs';
+
+/**
+ * @returns an Observable that proxies subscriptions to observables provided as arguments.
+ * Arguments are subscribed to in order they are provided.
+ */
+export const createStubObservable = <T>(...calls: Observable<T>[]) => {
+  let numCall = 0;
+  return new Observable<T>((subscriber) => {
+    const sub = calls[numCall++].subscribe(subscriber);
+    return () => sub.unsubscribe();
+  });
+};

packages/util-dev/src/index.ts

@@ -7,6 +7,7 @@ export * from './util';
 export * from './createStubStakePoolProvider';
 export * from './testScheduler';
 export * from './createStubUtxoProvider';
+export * from './createStubObservable';
 export * from './createGenericMockServer';
 export * from './dataGeneration';
 export * from './eraSummaries';

packages/util-dev/test/createStubObservable.test.ts

@@ -0,0 +1,15 @@
+import { concat } from 'rxjs';
+import { createStubObservable, createTestScheduler } from '../src';
+
+describe('createStubObservable', () => {
+  it('returns an observable that subscribes to observables provided as arguments in order', () => {
+    createTestScheduler().run(({ cold, expectObservable, expectSubscriptions }) => {
+      const a$ = cold('a|');
+      const b$ = cold('b|');
+      const target$ = createStubObservable(a$, b$);
+      expectObservable(concat(target$, target$)).toBe('ab|');
+      expectSubscriptions(a$.subscriptions).toBe('^!');
+      expectSubscriptions(b$.subscriptions).toBe('-^!');
+    });
+  });
+});

packages/wallet/test/services/TipTracker.test.ts

@@ -3,17 +3,9 @@ import { ConnectionStatus, TipTracker } from '../../src/services';
 import { InMemoryDocumentStore } from '../../src/persistence';
 import { Milliseconds, SyncStatus } from '../../src';
 import { Observable, firstValueFrom, of } from 'rxjs';
-import { createTestScheduler } from '@cardano-sdk/util-dev';
+import { createStubObservable, createTestScheduler } from '@cardano-sdk/util-dev';
 import { dummyLogger } from 'ts-log';
 
-const stubObservableProvider = <T>(...calls: Observable<T>[]) => {
-  let numCall = 0;
-  return new Observable<T>((subscriber) => {
-    const sub = calls[numCall++].subscribe(subscriber);
-    return () => sub.unsubscribe();
-  });
-};
-
 const mockTips = {
   a: { hash: 'ha' },
   b: { hash: 'hb' },
@@ -37,7 +29,7 @@ describe('TipTracker', () => {
   it('calls the provider immediately, only emitting distinct values, with throttling', () => {
     createTestScheduler().run(({ cold, expectObservable }) => {
       const syncStatus: Partial<SyncStatus> = { isSettled$: cold('---a---bc--d|') };
-      const provider$ = stubObservableProvider<Cardano.Tip>(
+      const provider$ = createStubObservable<Cardano.Tip>(
         cold('-x|', mockTips),
         cold('--a|', mockTips),
         cold('--b|', mockTips),
@@ -85,7 +77,7 @@ describe('TipTracker', () => {
     store.set = jest.fn().mockImplementation(store.set.bind(store));
     createTestScheduler().run(({ cold, expectObservable }) => {
       const syncStatus: Partial<SyncStatus> = { isSettled$: cold('---a---b|') };
-      const provider$ = stubObservableProvider<Cardano.Tip>(
+      const provider$ = createStubObservable<Cardano.Tip>(
         cold('-y|', mockTips),
         cold('--a|', mockTips),
         cold('-ab|', mockTips)
@@ -108,7 +100,7 @@ describe('TipTracker', () => {
   it('times out trigger$ with maxPollInterval, then listens for trigger$ again', () => {
     createTestScheduler().run(({ cold, hot, expectObservable }) => {
       const syncStatus: Partial<SyncStatus> = { isSettled$: hot('10ms a|') };
-      const provider$ = stubObservableProvider<Cardano.Tip>(
+      const provider$ = createStubObservable<Cardano.Tip>(
         cold('-a|', mockTips),
         cold('-b|', mockTips),
         cold('-c|', mockTips)
@@ -135,7 +127,7 @@ describe('TipTracker', () => {
         d: ConnectionStatus.down,
         p: ConnectionStatus.up
       });
-      const provider$ = stubObservableProvider<Cardano.Tip>(cold('x|', mockTips), cold('a|', mockTips));
+      const provider$ = createStubObservable<Cardano.Tip>(cold('x|', mockTips), cold('a|', mockTips));
       const tracker$ = new TipTracker({
         connectionStatus$: connectionStatusMock$,
         logger,