Fixes a bug where deployment node instances could set to a non-positive integer.

Author: simonbrowndotje

Structurizr.Core.Tests/Model/DeploymentNodeTests.cs

@@ -221,6 +221,45 @@ public void Test_GetInfrastructureNodeWithName_ReturnsTheNamedDeploymentNode_Whe
             Assert.Same(child, parent.GetInfrastructureNodeWithName("child"));
         }
 
+        [Fact]
+        public void Test_Instances()
+        {
+            DeploymentNode deploymentNode = new DeploymentNode();
+            deploymentNode.Instances = 8;
+
+            Assert.Equal(8, deploymentNode.Instances);
+        }
+
+        [Fact]
+        public void Test_Instances_ThrowsAnException_WhenZeroIsSpecified()
+        {
+            try
+            {
+                DeploymentNode deploymentNode = new DeploymentNode();
+                deploymentNode.Instances = 0;
+                throw new TestFailedException();
+            }
+            catch (ArgumentException ae)
+            {
+                Assert.Equal("Number of instances must be a positive integer.", ae.Message);
+            }
+        }
+
+        [Fact]
+        public void Test_Instances_ThrowsAnException_WhenANegativeNumberIsSpecified()
+        {
+            try
+            {
+                DeploymentNode deploymentNode = new DeploymentNode();
+                deploymentNode.Instances = -1;
+                throw new TestFailedException();
+            }
+            catch (ArgumentException ae)
+            {
+                Assert.Equal("Number of instances must be a positive integer.", ae.Message);
+            }
+        }
+
     }
-    
+
 }

Structurizr.Core/Model/DeploymentNode.cs

@@ -34,8 +34,26 @@ public override Element Parent
         [DataMember(Name = "technology", EmitDefaultValue = false)]
         public string Technology { get; set; }
 
+        private int _instances = 1;
+
         [DataMember(Name = "instances", EmitDefaultValue = false)]
-        public int Instances { get; set; }
+        public int Instances
+        {
+            get
+            {
+                return _instances;
+            }
+
+            set
+            {
+                if (value < 1)
+                {
+                    throw new ArgumentException("Number of instances must be a positive integer.");
+                }
+
+                _instances = value;
+            }
+        }
 
         private HashSet<DeploymentNode> _children;