Ensure vertices with duplicate keys are not added to graph

Author: mafinar-cmb

lib/graph/vertex.dart

@@ -87,14 +87,24 @@ class Vertex<T> {
 
   @override
   String toString() => key;
+
+  // ignore: avoid_equals_and_hash_code_on_mutable_classes
+  bool operator ==(Object other) => other is Vertex && key == other.key;
+
+  // ignore: avoid_equals_and_hash_code_on_mutable_classes
+  int get hashCode => key.hashCode;
 }
 
 /// Unlocks a set of vertices
 void unlockVertices(Set<Vertex> vertices) {
-  vertices.forEach((v) => v.unlock());
+  for (var vertex in vertices) {
+    vertex.unlock();
+  }
 }
 
 /// Locks a set of vertices
 void lockVertices(Set<Vertex> vertices) {
-  vertices.forEach((v) => v.lock());
+  for (var vertex in vertices) {
+    vertex.lock();
+  }
 }

test/graph/graph_test.dart

@@ -91,8 +91,10 @@ void main() {
   });
 
   test('Does not add vertex with existing key', () {
+    var aDuplicate = Vertex(a.key);
     expect(simpleGraph.numberOfVertices, equals(6));
     expect(simpleGraph.addVertex(a), isFalse);
+    expect(simpleGraph.addVertex(aDuplicate), isFalse);
     expect(simpleGraph.numberOfVertices, equals(6));
   });
 

test/graph/vertex_test.dart

@@ -14,7 +14,7 @@ void main() {
 
   void _initializeVertices() {
     root = Vertex('A');
-    rootWithValue = Vertex('a', 'Wake up');
+    rootWithValue = Vertex('i', 'Wake up');
     connectedVertex = Vertex('0');
     toBeAdded = Vertex('1');
     anotherVertex = Vertex('2');
@@ -46,7 +46,7 @@ void main() {
   test('Initialization of a node', () {
     expect(root.key, equals('A'));
     expect(root.value, equals('A'));
-    expect(rootWithValue.key, equals('a'));
+    expect(rootWithValue.key, equals('i'));
     expect(rootWithValue.value, equals('Wake up'));
   });
 
@@ -59,11 +59,17 @@ void main() {
     expect(c.incomingVertices.contains(root), isTrue);
   });
 
-  test('Unsuccessfully add a vertex', () {
-    root.addConnection(b);
+  test('Cannot add vertex that already exists', () {
+    expect(root.addConnection(b), isTrue);
     expect(root.addConnection(b), isFalse);
   });
 
+  test('Cannot add vertex with the same key', () {
+    expect(root.addConnection(b), isTrue);
+    var bDuplicate = Vertex(b.key)..unlock();
+    expect(root.addConnection(bDuplicate), isFalse);
+  });
+
   test('Successfully remove a vertex', () {
     expect(toBeAdded.incomingVertices.isEmpty, isFalse);
     expect(connectedVertex.removeConnection(toBeAdded), isTrue);