test(mergeMap): add failing test

spec/operators/mergeMap-spec.ts

@@ -1,6 +1,6 @@
 import { expect } from 'chai';
-import { mergeMap, map } from 'rxjs/operators';
-import { asapScheduler, defer, Observable, from, of } from 'rxjs';
+import { mergeMap, map, mapTo } from 'rxjs/operators';
+import { asapScheduler, concat, defer, Observable, from, of, timer } from 'rxjs';
 import { hot, cold, expectObservable, expectSubscriptions } from '../helpers/marble-testing';
 
 declare const type: Function;
@@ -717,7 +717,7 @@ describe('mergeMap', () => {
  // Added as a failing test when investigating:
  // https://github.com/ReactiveX/rxjs/issues/4071
 
- const results: any[] = [];
+ const results: (number | string)[] = [];
 
  of(1).pipe(
  mergeMap(() => defer(() =>
@@ -744,7 +744,7 @@ describe('mergeMap', () => {
  // Added as a failing test when investigating:
  // https://github.com/ReactiveX/rxjs/issues/4071
 
- const results: any[] = [];
+ const results: (number | string)[] = [];
 
  of(1).pipe(
  mergeMap(() =>
@@ -764,6 +764,30 @@ describe('mergeMap', () => {
  }, 0);
  });
 
+ it('should support wrapped sources', (done: MochaDone) => {
+
+ // Added as a failing test when investigating:
+ // https://github.com/ReactiveX/rxjs/issues/4095
+
+ const results: (number | string)[] = [];
+
+ const wrapped = new Observable<number>(subscriber => {
+ const subscription = timer(0, asapScheduler).pipe(mapTo(42)).subscribe(subscriber);
+ return () => subscription.unsubscribe();
+ });
+ wrapped.pipe(
+ mergeMap(value => concat(of(value), timer(0, asapScheduler).pipe(mapTo(value))))
+ ).subscribe({
+ next(value) { results.push(value); },
+ complete() { results.push('done'); }
+ });
+
+ setTimeout(() => {
+ expect(results).to.deep.equal([42, 42, 'done']);
+ done();
+ }, 0);
+ });
+
  type('should support type signatures', () => {
  let o: Observable<number>;