diff --git a/akka-stream-tests/src/test/java/akka/stream/javadsl/GraphDslTest.java b/akka-stream-tests/src/test/java/akka/stream/javadsl/GraphDslTest.java
index 570171a9cc..b620eb88d7 100644
--- a/akka-stream-tests/src/test/java/akka/stream/javadsl/GraphDslTest.java
+++ b/akka-stream-tests/src/test/java/akka/stream/javadsl/GraphDslTest.java
@@ -10,19 +10,19 @@ import akka.japi.Pair;
 import akka.stream.*;
 import akka.testkit.AkkaJUnitActorSystemResource;
 import akka.testkit.AkkaSpec;
+import org.junit.Assert;
 import org.junit.ClassRule;
 import org.junit.Test;
-import scala.collection.Seq;
 
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.HashSet;
 import java.util.List;
 import java.util.concurrent.CompletionStage;
 import java.util.concurrent.TimeUnit;
 
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertTrue;
 
 public class GraphDslTest extends StreamTest {
@@ -78,29 +78,33 @@ public class GraphDslTest extends StreamTest {
   @Test
   @SuppressWarnings("unused")
   public void demonstrateConnectErrors() {
-    try {
-      // #simple-graph
-      final RunnableGraph<NotUsed> g =
-          RunnableGraph.<NotUsed>fromGraph(
-              GraphDSL.create(
-                  (b) -> {
-                    final SourceShape<Integer> source1 =
-                        b.add(Source.from(Arrays.asList(1, 2, 3, 4, 5)));
-                    final SourceShape<Integer> source2 =
-                        b.add(Source.from(Arrays.asList(1, 2, 3, 4, 5)));
-                    final FanInShape2<Integer, Integer, Pair<Integer, Integer>> zip =
-                        b.add(Zip.create());
-                    b.from(source1).toInlet(zip.in0());
-                    b.from(source2).toInlet(zip.in1());
-                    return ClosedShape.getInstance();
-                  }));
-      // unconnected zip.out (!) => "The inlets [] and outlets [] must correspond to the inlets []
-      // and outlets [ZipWith2.out]"
-      // #simple-graph
-      org.junit.Assert.fail("expected IllegalArgumentException");
-    } catch (IllegalStateException e) {
-      assertTrue(e != null && e.getMessage() != null && e.getMessage().contains("ZipWith2.out"));
-    }
+    IllegalStateException exception =
+        Assert.assertThrows(
+            "expected IllegalStateException",
+            IllegalStateException.class,
+            () -> {
+              // #simple-graph
+              final RunnableGraph<NotUsed> g =
+                  RunnableGraph.fromGraph(
+                      GraphDSL.create(
+                          (b) -> {
+                            final SourceShape<Integer> source1 =
+                                b.add(Source.from(Arrays.asList(1, 2, 3, 4, 5)));
+                            final SourceShape<Integer> source2 =
+                                b.add(Source.from(Arrays.asList(1, 2, 3, 4, 5)));
+                            final FanInShape2<Integer, Integer, Pair<Integer, Integer>> zip =
+                                b.add(Zip.create());
+                            b.from(source1).toInlet(zip.in0());
+                            b.from(source2).toInlet(zip.in1());
+                            return ClosedShape.getInstance();
+                          }));
+              // unconnected zip.out (!) => "The inlets [] and outlets [] must correspond to the
+              // inlets []
+              // and outlets [ZipWith2.out]"
+              // #simple-graph
+            });
+    assertNotNull(exception.getMessage());
+    assertTrue(exception.getMessage().contains("ZipWith2.out"));
   }
 
   @Test
@@ -112,7 +116,7 @@ public class GraphDslTest extends StreamTest {
         Flow.of(Integer.class).map(elem -> elem * 2);
 
     final RunnableGraph<Pair<CompletionStage<Integer>, CompletionStage<Integer>>> g =
-        RunnableGraph.<Pair<CompletionStage<Integer>, CompletionStage<Integer>>>fromGraph(
+        RunnableGraph.fromGraph(
             GraphDSL.create(
                 topHeadSink, // import this sink into the graph
                 bottomHeadSink, // and this as well
@@ -137,7 +141,7 @@ public class GraphDslTest extends StreamTest {
   public void demonstrateMatValue() throws Exception {
     // #graph-dsl-matvalue
     final Sink<Integer, CompletionStage<Integer>> foldSink =
-        Sink.<Integer, Integer>fold(
+        Sink.fold(
             0,
             (a, b) -> {
               return a + b;
@@ -222,10 +226,9 @@ public class GraphDslTest extends StreamTest {
   public void canUseMapMaterializedValueOnGraphs() {
     Graph<SourceShape<Object>, NotUsed> srcGraph = Source.empty();
     Graph<SourceShape<Object>, Pair<NotUsed, NotUsed>> mappedMatValueSrcGraph =
-        Graph.mapMaterializedValue(
-            srcGraph, notUsed -> new Pair<NotUsed, NotUsed>(notUsed, notUsed));
+        Graph.mapMaterializedValue(srcGraph, notUsed -> new Pair<>(notUsed, notUsed));
     Sink<Object, CompletionStage<Done>> snk = Sink.ignore();
     Pair<NotUsed, NotUsed> pair = Source.fromGraph(mappedMatValueSrcGraph).to(snk).run(system);
-    assertEquals(pair, new Pair<NotUsed, NotUsed>(NotUsed.getInstance(), NotUsed.getInstance()));
+    assertEquals(pair, new Pair<>(NotUsed.getInstance(), NotUsed.getInstance()));
   }
 }
diff --git a/akka-stream-tests/src/test/java/akka/stream/javadsl/TcpTest.java b/akka-stream-tests/src/test/java/akka/stream/javadsl/TcpTest.java
index db345ba5f8..5d9e412922 100644
--- a/akka-stream-tests/src/test/java/akka/stream/javadsl/TcpTest.java
+++ b/akka-stream-tests/src/test/java/akka/stream/javadsl/TcpTest.java
@@ -20,6 +20,8 @@ import akka.testkit.javadsl.EventFilter;
 import akka.testkit.javadsl.TestKit;
 import akka.util.ByteString;
 import static akka.util.ByteString.emptyByteString;
+
+import org.junit.Assert;
 import org.junit.ClassRule;
 import org.junit.Test;
 
@@ -69,7 +71,7 @@ public class TcpTest extends StreamTest {
             }
           });
 
-  final List<ByteString> testInput = new ArrayList<ByteString>();
+  final List<ByteString> testInput = new ArrayList<>();
 
   {
     for (char c = 'a'; c <= 'z'; c++) {
@@ -127,22 +129,20 @@ public class TcpTest extends StreamTest {
             .occurrences(1)
             .intercept(
                 () -> {
-                  try {
-                    binding
-                        .to(echoHandler)
-                        .run(system)
-                        .toCompletableFuture()
-                        .get(5, TimeUnit.SECONDS);
-                    assertTrue("Expected BindFailedException, but nothing was reported", false);
-                  } catch (ExecutionException e) {
-                    if (e.getCause() instanceof BindFailedException) {
-                    } // all good
-                    else throw new AssertionError("failed", e);
-                    // expected
-                    b.unbind();
-                  } catch (Exception e) {
-                    throw new AssertionError("failed", e);
-                  }
+                  ExecutionException executionException =
+                      Assert.assertThrows(
+                          "CompletableFuture.get() should throw ExecutionException",
+                          ExecutionException.class,
+                          () ->
+                              binding
+                                  .to(echoHandler)
+                                  .run(system)
+                                  .toCompletableFuture()
+                                  .get(5, TimeUnit.SECONDS));
+                  assertTrue(
+                      "The cause of ExecutionException should be instanceof BindFailedException",
+                      executionException.getCause() instanceof BindFailedException);
+                  b.unbind();
                   return null;
                 });
       }
@@ -150,26 +150,27 @@ public class TcpTest extends StreamTest {
   }
 
   @Test
-  public void mustReportClientConnectFailure() throws Throwable {
+  public void mustReportClientConnectFailure() {
     final InetSocketAddress serverAddress = SocketUtil.notBoundServerAddress();
-    try {
-      try {
-        Source.from(testInput)
-            .viaMat(
-                Tcp.get(system)
-                    .outgoingConnection(serverAddress.getHostString(), serverAddress.getPort()),
-                Keep.right())
-            .to(Sink.<ByteString>ignore())
-            .run(system)
-            .toCompletableFuture()
-            .get(5, TimeUnit.SECONDS);
-        assertTrue("Expected StreamTcpException, but nothing was reported", false);
-      } catch (ExecutionException e) {
-        throw e.getCause();
-      }
-    } catch (StreamTcpException e) {
-      // expected
-    }
+    ExecutionException executionException =
+        Assert.assertThrows(
+            "CompletableFuture.get() should throw ExecutionException",
+            ExecutionException.class,
+            () ->
+                Source.from(testInput)
+                    .viaMat(
+                        Tcp.get(system)
+                            .outgoingConnection(
+                                serverAddress.getHostString(), serverAddress.getPort()),
+                        Keep.right())
+                    .to(Sink.ignore())
+                    .run(system)
+                    .toCompletableFuture()
+                    .get(5, TimeUnit.SECONDS));
+    assertEquals(
+        "The cause of ExecutionException should be StreamTcpException",
+        StreamTcpException.class,
+        executionException.getCause().getClass());
   }
 
   // compile only sample