message: test(docs-infra): add missing test for the `rx-library` docs example
  This commit adds an extra test for the `retry-on-error` snippet of the
  `rx-library` docs example to ensure it can successfully recover after a
  couple of failed attempts.
  This commit addresses comment
  PR Close
diff: import { of, throwError } from 'rxjs';
  -import { tap } from 'rxjs/operators';
  +import { mergeMap, tap } from 'rxjs/operators';
  import { docRegionDefault } from './retry-on-error';
  describe('retry-on-error', () => {
  @@ -34,6 +34,30 @@ describe('retry-on-error', () => {
  ]);
  });
  + it('should return the response if the request succeeds upon retrying', () => {
  + // Fail on the first two requests, but succeed from the 3rd onwards.
  + let failCount = 2;
  + const ajax = () => of(null).pipe(
  + tap(() => mockConsole.log('Subscribed to AJAX')),
  + // Fail on the first 2 requests, but succeed from the 3rd onwards.
  + mergeMap(() => {
  + if (failCount > 0) {
  + failCount--;
  + return throwError('Test error');
  + }
  + return of({ response: { foo: 'bar' } });
  + }),
  + );
  +
  + docRegionDefault(mockConsole, ajax);
  + expect(mockConsole.log.calls.allArgs()).toEqual([
  + ['Subscribed to AJAX'], // Initial request | 1st attempt overall
  + ['Subscribed to AJAX'], // 1st retry attempt | 2nd attempt overall
  + ['Subscribed to AJAX'], // 2nd retry attempt | 3rd attempt overall
  + ['data: ', { foo: 'bar' }],
  + ]);
  + });
  +
  it('should return an empty array when the ajax observable throws an error', () => {
  const ajax = () => throwError('Test Error');
  