test: add a test for deferred jobs

Just one more bit of coverage.

packages/angular_devkit/core/src/experimental/jobs/simple-scheduler_spec.ts

@@ -590,5 +590,36 @@ describe('SimpleScheduler', () => {
       expect(await job.output.toPromise()).toBe(103);
       expect(outputs).toEqual([101, 103]);
     });
+
+    it('works deferred', async () => {
+      // This is a more complex test. The job returns an output deferred from the input
+      registry.register(
+        'job',
+        createJobHandler<number, number, number>((argument, context) => {
+          return new Observable<number>(subscriber => {
+            context.input.subscribe(x => {
+              if (x === null) {
+                setTimeout(() => subscriber.complete(), 10);
+              } else {
+                setTimeout(() => subscriber.next(parseInt('' + x) + argument), x);
+              }
+            });
+          });
+        }),
+      );
+
+      const job = scheduler.schedule('job', 100);
+      const outputs: number[] = [];
+
+      job.output.subscribe(x => outputs.push(x as number));
+
+      job.input.next(1);
+      job.input.next(2);
+      job.input.next(3);
+      job.input.next(null);
+
+      expect(await job.output.toPromise()).toBe(103);
+      expect(outputs).toEqual(jasmine.arrayWithExactContents([101, 102, 103]));
+    });
   });
 });