[65-74] SubscriberSinkSpec (#6613)

* [65-74] `SubscriberSinkSpec`

* Changes to `async/await`

Author: eaba

src/core/Akka.Streams.Tests/Dsl/SubscriberSinkSpec.cs

@@ -6,6 +6,7 @@
 //-----------------------------------------------------------------------
 
 using System.Linq;
+using System.Threading.Tasks;
 using Akka.Streams.Dsl;
 using Akka.Streams.TestKit;
 using Akka.TestKit;
@@ -25,19 +26,18 @@ public SubscriberSinkSpec(ITestOutputHelper helper = null) : base(helper)
         }
 
         [Fact]
-        public void A_Flow_with_SubscriberSink_must_publish_elements_to_the_subscriber()
+        public async Task A_Flow_with_SubscriberSink_must_publish_elements_to_the_subscriber()
         {
-            this.AssertAllStagesStopped(() =>
-            {
+            await this.AssertAllStagesStoppedAsync(async() => {
                 var c = this.CreateManualSubscriberProbe<int>();
                 Source.From(Enumerable.Range(1, 3)).To(Sink.FromSubscriber(c)).Run(Materializer);
 
-                var s = c.ExpectSubscription();
+                var s = await c.ExpectSubscriptionAsync();
                 s.Request(3);
-                c.ExpectNext(1);
-                c.ExpectNext(2);
-                c.ExpectNext(3);
-                c.ExpectComplete();
+                await c.ExpectNextAsync(1);
+                await c.ExpectNextAsync(2);
+                await c.ExpectNextAsync(3);
+                await c.ExpectCompleteAsync();
             }, Materializer);
         }
     }