fix remove vertex

core-java-modules/core-java/src/main/java/com/baeldung/graph/Graph.java

@@ -19,7 +19,7 @@ public class Graph {
 
     void removeVertex(String label) {
         Vertex v = new Vertex(label);
-        adjVertices.values().stream().map(e -> e.remove(v)).collect(Collectors.toList());
+        adjVertices.values().stream().forEach(e -> e.remove(v));
         adjVertices.remove(new Vertex(label));
     }
 

core-java-modules/core-java/src/test/java/com/baeldung/graph/GraphUnitTest.java

@@ -1,20 +1,31 @@
 package com.baeldung.graph;
 
-import org.junit.Assert;
+import static org.junit.Assert.assertEquals;
 import org.junit.Test;
 
-public class GraphTraversalUnitTest {
+public class GraphUnitTest {
     @Test
     public void givenAGraph_whenTraversingDepthFirst_thenExpectedResult() {
         Graph graph = createGraph();
-        Assert.assertEquals("[Bob, Rob, Maria, Alice, Mark]", 
+        assertEquals("[Bob, Rob, Maria, Alice, Mark]", 
             GraphTraversal.depthFirstTraversal(graph, "Bob").toString());
     }
     
     @Test
     public void givenAGraph_whenTraversingBreadthFirst_thenExpectedResult() {
         Graph graph = createGraph();
-        Assert.assertEquals("[Bob, Alice, Rob, Mark, Maria]", 
+       assertEquals("[Bob, Alice, Rob, Mark, Maria]", 
+            GraphTraversal.breadthFirstTraversal(graph, "Bob").toString());
+    }
+    
+    @Test
+    public void givenAGraph_whenRemoveVertex_thenVertedNotFound() {
+        Graph graph = createGraph();
+        assertEquals("[Bob, Alice, Rob, Mark, Maria]", 
+            GraphTraversal.breadthFirstTraversal(graph, "Bob").toString());
+        
+        graph.removeVertex("Maria");
+        assertEquals("[Bob, Alice, Rob, Mark]", 
             GraphTraversal.breadthFirstTraversal(graph, "Bob").toString());
     }