ReactiveX · dynst · Oct 27, 2025
diff --git a/packages/rxjs/spec/Observable-spec.ts b/packages/rxjs/spec/Observable-spec.ts
@@ -3,7 +3,7 @@ import { expect } from 'chai';
 import { Observable, config, Subscription, Subject, of, throwError, EMPTY } from 'rxjs';
 import { map, tap, catchError } from 'rxjs/operators';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from './helpers/observableMatcher';
+import { observableMatcher } from './helpers/observableMatcher.js';
 
 // function expectFullObserver(val: any) {
 //   expect(val).to.be.a('object');

diff --git a/packages/rxjs/spec/Subject-spec.ts b/packages/rxjs/spec/Subject-spec.ts
@@ -3,7 +3,7 @@ import type { Subscription} from 'rxjs';
 import { Subject, Observable, AsyncSubject, of, config, Subscriber, noop, operate } from 'rxjs';
 import { delay } from 'rxjs/operators';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from './helpers/observableMatcher';
+import { observableMatcher } from './helpers/observableMatcher.js';
 
 /** @test {Subject} */
 describe('Subject', () => {

diff --git a/packages/rxjs/spec/Subscriber-spec.ts b/packages/rxjs/spec/Subscriber-spec.ts
@@ -2,8 +2,8 @@ import { expect } from 'chai';
 import type { Observer} from 'rxjs';
 import { Subscriber, Observable, of, config, operate } from 'rxjs';
 import * as sinon from 'sinon';
-import { asInteropSubscriber } from './helpers/interop-helper';
-import { getRegisteredFinalizers } from './helpers/subscription';
+import { asInteropSubscriber } from './helpers/interop-helper.js';
+import { getRegisteredFinalizers } from './helpers/subscription.js';
 
 /** @test {Subscriber} */
 describe('Subscriber', () => {

diff --git a/packages/rxjs/spec/helpers/interop-helper-spec.ts b/packages/rxjs/spec/helpers/interop-helper-spec.ts
@@ -1,6 +1,6 @@
 import { expect } from 'chai';
 import { Observable, of, Subscriber } from 'rxjs';
-import { asInteropObservable, asInteropSubscriber } from './interop-helper';
+import { asInteropObservable, asInteropSubscriber } from './interop-helper.js';
 
 describe('interop helper', () => {
   it('should simulate interop observables', () => {

diff --git a/packages/rxjs/spec/helpers/marble-testing.ts b/packages/rxjs/spec/helpers/marble-testing.ts
@@ -1,8 +1,8 @@
 import type { Observable } from 'rxjs';
-import type { SubscriptionLog } from '../../src/internal/testing/subscription-logging';
-import type { ColdObservable } from '../../src/internal/testing/ColdObservable';
-import type { HotObservable } from '../../src/internal/testing/HotObservable';
-import type { observableToBeFn, subscriptionLogsToBeFn } from '../../src/internal/testing/TestScheduler';
+import type { SubscriptionLog } from '../../src/internal/testing/subscription-logging.js';
+import type { ColdObservable } from '../../src/internal/testing/ColdObservable.js';
+import type { HotObservable } from '../../src/internal/testing/HotObservable.js';
+import type { observableToBeFn, subscriptionLogsToBeFn } from '../../src/internal/testing/TestScheduler.js';
 
 declare const global: any;
 

diff --git a/packages/rxjs/spec/observables/bindCallback-spec.ts b/packages/rxjs/spec/observables/bindCallback-spec.ts
@@ -3,7 +3,7 @@ import { expect } from 'chai';
 import * as sinon from 'sinon';
 import { bindCallback } from 'rxjs';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 /** @test {bindCallback} */
 describe('bindCallback', () => {

diff --git a/packages/rxjs/spec/observables/bindNodeCallback-spec.ts b/packages/rxjs/spec/observables/bindNodeCallback-spec.ts
@@ -3,7 +3,7 @@ import { expect } from 'chai';
 import * as sinon from 'sinon';
 import { bindNodeCallback } from 'rxjs';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 /** @test {bindNodeCallback} */
 describe('bindNodeCallback', () => {

diff --git a/packages/rxjs/spec/observables/combineLatest-spec.ts b/packages/rxjs/spec/observables/combineLatest-spec.ts
@@ -2,7 +2,7 @@ import { expect } from 'chai';
 import { combineLatest, of } from 'rxjs';
 import { map, mergeMap } from 'rxjs/operators';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 /** @test {combineLatest} */
 describe('static combineLatest', () => {

diff --git a/packages/rxjs/spec/observables/concat-spec.ts b/packages/rxjs/spec/observables/concat-spec.ts
@@ -1,10 +1,10 @@
 /** @prettier */
 import { expect } from 'chai';
-import { lowerCaseO } from '../helpers/test-helper';
+import { lowerCaseO } from '../helpers/test-helper.js';
 import { asyncScheduler, queueScheduler, concat, of, scheduled, defer, Observable } from 'rxjs';
 import { mergeMap } from 'rxjs/operators';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 /** @test {concat} */
 describe('static concat', () => {

diff --git a/packages/rxjs/spec/observables/connectable-spec.ts b/packages/rxjs/spec/observables/connectable-spec.ts
@@ -2,7 +2,7 @@
 import { expect } from 'chai';
 import { connectable, of, ReplaySubject } from 'rxjs';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 describe('connectable', () => {
   let testScheduler: TestScheduler;

diff --git a/packages/rxjs/spec/observables/defer-spec.ts b/packages/rxjs/spec/observables/defer-spec.ts
@@ -3,7 +3,7 @@ import { expect } from 'chai';
 import { defer, of } from 'rxjs';
 import { mergeMap } from 'rxjs/operators';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 /** @test {defer} */
 describe('defer', () => {

diff --git a/packages/rxjs/spec/observables/dom/animationFrames-spec.ts b/packages/rxjs/spec/observables/dom/animationFrames-spec.ts
@@ -4,7 +4,7 @@ import * as sinon from 'sinon';
 import { animationFrames } from 'rxjs';
 import { mergeMapTo, take, takeUntil } from 'rxjs/operators';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../../helpers/observableMatcher';
+import { observableMatcher } from '../../helpers/observableMatcher.js';
 import { animationFrameProvider } from 'rxjs/internal/scheduler/animationFrameProvider';
 
 describe('animationFrames', () => {

diff --git a/packages/rxjs/spec/observables/empty-spec.ts b/packages/rxjs/spec/observables/empty-spec.ts
@@ -2,7 +2,7 @@
 import { expect } from 'chai';
 import { EMPTY } from 'rxjs';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 /** @test {empty} */
 describe('empty', () => {

diff --git a/packages/rxjs/spec/observables/forkJoin-spec.ts b/packages/rxjs/spec/observables/forkJoin-spec.ts
@@ -1,9 +1,9 @@
 /** @prettier */
 import { expect } from 'chai';
 import { EmptyError, finalize, forkJoin, map, of, timer } from 'rxjs';
-import { lowerCaseO } from '../helpers/test-helper';
+import { lowerCaseO } from '../helpers/test-helper.js';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 /** @test {forkJoin} */
 describe('forkJoin', () => {

diff --git a/packages/rxjs/spec/observables/from-spec.ts b/packages/rxjs/spec/observables/from-spec.ts
@@ -5,7 +5,7 @@ import type { Observer, Subscription } from 'rxjs';
 import { of, from, Subject, noop } from 'rxjs';
 import { first, concatMap, delay, take, tap } from 'rxjs/operators';
 import { ReadableStream } from 'web-streams-polyfill';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 function getArguments<T>(...args: T[]) {
   return args;

diff --git a/packages/rxjs/spec/observables/fromEvent-spec.ts b/packages/rxjs/spec/observables/fromEvent-spec.ts
@@ -3,7 +3,7 @@ import { expect } from 'chai';
 import { fromEvent, NEVER, timer } from 'rxjs';
 import { mapTo, take, concatWith } from 'rxjs/operators';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 /** @test {fromEvent} */
 describe('fromEvent', () => {

diff --git a/packages/rxjs/spec/observables/fromEventPattern-spec.ts b/packages/rxjs/spec/observables/fromEventPattern-spec.ts
@@ -5,7 +5,7 @@ import * as sinon from 'sinon';
 import { fromEventPattern, noop, NEVER, timer } from 'rxjs';
 import { mapTo, take, concatWith } from 'rxjs/operators';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 /** @test {fromEventPattern} */
 describe('fromEventPattern', () => {

diff --git a/packages/rxjs/spec/observables/generate-spec.ts b/packages/rxjs/spec/observables/generate-spec.ts
@@ -4,7 +4,7 @@ import { expect } from 'chai';
 import { generate } from 'rxjs';
 import { take } from 'rxjs/operators';
 import { Subscriber } from '@rxjs/observable';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 function err(): any {
   throw 'error';

diff --git a/packages/rxjs/spec/observables/if-spec.ts b/packages/rxjs/spec/observables/if-spec.ts
@@ -2,7 +2,7 @@
 import { expect } from 'chai';
 import { iif, of } from 'rxjs';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 describe('iif', () => {
   let rxTestScheduler: TestScheduler;

diff --git a/packages/rxjs/spec/observables/interval-spec.ts b/packages/rxjs/spec/observables/interval-spec.ts
@@ -4,7 +4,7 @@ import { NEVER, interval, asapScheduler, animationFrameScheduler, queueScheduler
 import { TestScheduler } from 'rxjs/testing';
 import { take } from 'rxjs/operators';
 import * as sinon from 'sinon';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 /** @test {interval} */
 describe('interval', () => {

diff --git a/packages/rxjs/spec/observables/merge-spec.ts b/packages/rxjs/spec/observables/merge-spec.ts
@@ -1,10 +1,10 @@
 /** @prettier */
 import { expect } from 'chai';
-import { lowerCaseO } from '../helpers/test-helper';
+import { lowerCaseO } from '../helpers/test-helper.js';
 import { TestScheduler } from 'rxjs/testing';
 import { merge, of, Observable, defer, asyncScheduler } from 'rxjs';
 import { delay } from 'rxjs/operators';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 /** @test {merge} */
 describe('static merge(...observables)', () => {

diff --git a/packages/rxjs/spec/observables/never-spec.ts b/packages/rxjs/spec/observables/never-spec.ts
@@ -2,7 +2,7 @@
 import { NEVER } from 'rxjs';
 import { expect } from 'chai';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 /** @test {NEVER} */
 describe('NEVER', () => {

diff --git a/packages/rxjs/spec/observables/of-spec.ts b/packages/rxjs/spec/observables/of-spec.ts
@@ -3,7 +3,7 @@ import { expect } from 'chai';
 import { of } from 'rxjs';
 import { TestScheduler } from 'rxjs/testing';
 import { concatMap, delay, concatAll } from 'rxjs/operators';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 /** @test {of} */
 describe('of', () => {

diff --git a/packages/rxjs/spec/observables/onErrorResumeNext-spec.ts b/packages/rxjs/spec/observables/onErrorResumeNext-spec.ts
@@ -3,7 +3,7 @@ import { onErrorResumeNext, of } from 'rxjs';
 import { finalize } from 'rxjs/operators';
 import { expect } from 'chai';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 describe('onErrorResumeNext', () => {
   let rxTestScheduler: TestScheduler;

diff --git a/packages/rxjs/spec/observables/partition-spec.ts b/packages/rxjs/spec/observables/partition-spec.ts
@@ -4,7 +4,7 @@ import type { Observable} from 'rxjs';
 import { partition, of } from 'rxjs';
 import { mergeMap } from 'rxjs/operators';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 /** @test {partition} */
 describe('partition', () => {

diff --git a/packages/rxjs/spec/observables/race-spec.ts b/packages/rxjs/spec/observables/race-spec.ts
@@ -3,7 +3,7 @@ import { race, of } from 'rxjs';
 import { mergeMap } from 'rxjs/operators';
 import { expect } from 'chai';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 /** @test {race} */
 describe('race', () => {

diff --git a/packages/rxjs/spec/observables/range-spec.ts b/packages/rxjs/spec/observables/range-spec.ts
@@ -4,7 +4,7 @@ import * as sinon from 'sinon';
 import { asapScheduler as asap, range, of } from 'rxjs';
 import { TestScheduler } from 'rxjs/testing';
 import { concatMap, delay } from 'rxjs/operators';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 /** @test {range} */
 describe('range', () => {

diff --git a/packages/rxjs/spec/observables/throwError-spec.ts b/packages/rxjs/spec/observables/throwError-spec.ts
@@ -2,7 +2,7 @@
 import { expect } from 'chai';
 import { TestScheduler } from 'rxjs/testing';
 import { throwError } from 'rxjs';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 /** @test {throwError} */
 describe('throwError', () => {

diff --git a/packages/rxjs/spec/observables/timer-spec.ts b/packages/rxjs/spec/observables/timer-spec.ts
@@ -1,7 +1,7 @@
 import { timer, NEVER, merge } from 'rxjs';
 import { TestScheduler } from 'rxjs/testing';
 import { mergeMap, take, concatWith } from 'rxjs/operators';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 /** @test {timer} */
 describe('timer', () => {

diff --git a/packages/rxjs/spec/observables/zip-spec.ts b/packages/rxjs/spec/observables/zip-spec.ts
@@ -2,7 +2,7 @@
 import { expect } from 'chai';
 import { queueScheduler as rxQueueScheduler, zip, from, scheduled } from 'rxjs';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 const queueScheduler = rxQueueScheduler;
 

diff --git a/packages/rxjs/spec/operators/audit-spec.ts b/packages/rxjs/spec/operators/audit-spec.ts
@@ -2,7 +2,7 @@ import { expect } from 'chai';
 import { TestScheduler } from 'rxjs/testing';
 import { of, interval, EMPTY, Observable } from 'rxjs';
 import { audit, take, mergeMap } from 'rxjs/operators';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 /** @test {audit} */
 describe('audit operator', () => {

diff --git a/packages/rxjs/spec/operators/auditTime-spec.ts b/packages/rxjs/spec/operators/auditTime-spec.ts
@@ -2,7 +2,7 @@ import { expect } from 'chai';
 import { of } from 'rxjs';
 import { auditTime, mergeMap } from 'rxjs/operators';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 /** @test {auditTime} */
 describe('auditTime', () => {

diff --git a/packages/rxjs/spec/operators/buffer-spec.ts b/packages/rxjs/spec/operators/buffer-spec.ts
@@ -1,7 +1,7 @@
 import { buffer, mergeMap, take, window, toArray } from 'rxjs/operators';
 import { EMPTY, NEVER, throwError, of, Subject, interval } from 'rxjs';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 import { expect } from 'chai';
 
 /** @test {buffer} */

diff --git a/packages/rxjs/spec/operators/bufferCount-spec.ts b/packages/rxjs/spec/operators/bufferCount-spec.ts
@@ -2,7 +2,7 @@ import { expect } from 'chai';
 import { Subject, of, Observable } from 'rxjs';
 import { bufferCount, mergeMap, take } from 'rxjs/operators';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 /** @test {bufferCount} */
 describe('bufferCount operator', () => {

diff --git a/packages/rxjs/spec/operators/bufferTime-spec.ts b/packages/rxjs/spec/operators/bufferTime-spec.ts
@@ -1,7 +1,7 @@
 import { of, throwError, interval, scheduled, asapScheduler, Subject } from 'rxjs';
 import { bufferTime, mergeMap, take, tap } from 'rxjs/operators';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 import { expect } from 'chai';
 
 /** @test {bufferTime} */

diff --git a/packages/rxjs/spec/operators/bufferToggle-spec.ts b/packages/rxjs/spec/operators/bufferToggle-spec.ts
@@ -2,7 +2,7 @@ import { expect } from 'chai';
 import { of, concat, timer, EMPTY } from 'rxjs';
 import { bufferToggle, mergeMap, mapTo } from 'rxjs/operators';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 /** @test {bufferToggle} */
 describe('bufferToggle operator', () => {

diff --git a/packages/rxjs/spec/operators/bufferWhen-spec.ts b/packages/rxjs/spec/operators/bufferWhen-spec.ts
@@ -2,7 +2,7 @@ import { expect } from 'chai';
 import { of } from 'rxjs';
 import { bufferWhen, mergeMap, takeWhile } from 'rxjs/operators';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 /** @test {bufferWhen} */
 describe('bufferWhen operator', () => {

diff --git a/packages/rxjs/spec/operators/catchError-spec.ts b/packages/rxjs/spec/operators/catchError-spec.ts
@@ -2,10 +2,10 @@ import { expect } from 'chai';
 import { concat, defer, Observable, of, throwError, EMPTY, from } from 'rxjs';
 import { catchError, map, mergeMap, takeWhile, delay, take } from 'rxjs/operators';
 import * as sinon from 'sinon';
-import { createObservableInputs } from '../helpers/test-helper';
+import { createObservableInputs } from '../helpers/test-helper.js';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../helpers/observableMatcher';
-import { asInteropObservable } from '../helpers/interop-helper';
+import { observableMatcher } from '../helpers/observableMatcher.js';
+import { asInteropObservable } from '../helpers/interop-helper.js';
 
 /** @test {catch} */
 describe('catchError operator', () => {

diff --git a/packages/rxjs/spec/operators/combineLatestAll-spec.ts b/packages/rxjs/spec/operators/combineLatestAll-spec.ts
@@ -2,7 +2,7 @@ import { expect } from 'chai';
 import { queueScheduler, of, scheduled } from 'rxjs';
 import { combineLatestAll, mergeMap } from 'rxjs/operators';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 /** @test {combineLatestAll} */
 describe('combineLatestAll operator', () => {

diff --git a/packages/rxjs/spec/operators/combineLatestWith-spec.ts b/packages/rxjs/spec/operators/combineLatestWith-spec.ts
@@ -1,7 +1,7 @@
 import { of } from 'rxjs';
 import { combineLatestWith, mergeMap, distinct, count, map } from 'rxjs/operators';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 /** @test {combineLatestWith} */
 describe('combineLatestWith', () => {

diff --git a/packages/rxjs/spec/operators/concatAll-spec.ts b/packages/rxjs/spec/operators/concatAll-spec.ts
@@ -2,7 +2,7 @@ import { expect } from 'chai';
 import { from, throwError, of, scheduled, Observable, defer } from 'rxjs';
 import { concatAll, take, mergeMap, finalize, delay } from 'rxjs/operators';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 /** @test {concatAll} */
 describe('concatAll operator', () => {

diff --git a/packages/rxjs/spec/operators/concatMap-spec.ts b/packages/rxjs/spec/operators/concatMap-spec.ts
@@ -2,7 +2,7 @@ import { expect } from 'chai';
 import { of, from, Observable, defer } from 'rxjs';
 import { concatMap, mergeMap, map, take, finalize, delay } from 'rxjs/operators';
 import { TestScheduler } from 'rxjs/testing';
-import { observableMatcher } from '../helpers/observableMatcher';
+import { observableMatcher } from '../helpers/observableMatcher.js';
 
 /** @test {concatMap} */
 describe('Observable.prototype.concatMap', () => {