=str #18902 in tests (due to grouped+Sink.head) empty response stream would throw

akka-http-testkit/src/main/scala/akka/http/scaladsl/testkit/RouteTestResultComponent.scala

@@ -5,9 +5,11 @@
 package akka.http.scaladsl.testkit
 
 import java.util.concurrent.CountDownLatch
+import akka.dispatch.ExecutionContexts
+
 import scala.collection.immutable
 import scala.concurrent.duration._
-import scala.concurrent.ExecutionContext
+import scala.concurrent.{ Await, ExecutionContext }
 import akka.stream.Materializer
 import akka.stream.scaladsl._
 import akka.http.scaladsl.model.HttpEntity.ChunkStreamPart
@@ -95,7 +97,11 @@ trait RouteTestResultComponent {
     private def failNeitherCompletedNorRejected(): Nothing =
       failTest("Request was neither completed nor rejected within " + timeout)
 
-    private def awaitAllElements[T](data: Source[T, _]): immutable.Seq[T] =
-      data.grouped(100000).runWith(Sink.head).awaitResult(timeout)
+    private def awaitAllElements[T](data: Source[T, _]): immutable.Seq[T] = {
+      data.grouped(100000).runWith(Sink.head).recover({
+        case e: NoSuchElementException ⇒ Nil
+      })(ExecutionContexts.sameThreadExecutionContext)
+        .awaitResult(timeout)
+    }
   }
 }

akka-http-tests/src/test/scala/akka/http/scaladsl/server/StreamingResponseSpecs.scala

@@ -0,0 +1,29 @@
+/*
+ * Copyright (C) 2009-2015 Typesafe Inc. <http://www.typesafe.com>
+ */
+
+package akka.http.scaladsl.server
+
+import akka.http.scaladsl.model.{ ContentTypes, HttpEntity, HttpResponse, StatusCodes }
+import akka.stream.scaladsl.Source
+import akka.util.ByteString
+
+class StreamingResponseSpecs extends RoutingSpec {
+
+  "streaming ByteString responses" should {
+    "should render empty string if stream was empty" in {
+      import StatusCodes._
+
+      val src = Source.empty[ByteString]
+      val entity = HttpEntity.Chunked.fromData(ContentTypes.`application/json`, src)
+      val response = HttpResponse(status = StatusCodes.OK, entity = entity)
+      val route = complete(response)
+
+      Get() ~> route ~> check {
+        status should ===(OK)
+        responseAs[String] shouldEqual ""
+      }
+    }
+
+  }
+}