Added support for building NSubstitute proxies

Author: robdmoore

NTestDataBuilder.Tests/AsProxyTests.cs

@@ -0,0 +1,31 @@
+using System;
+using NSubstitute;
+using NTestDataBuilder.Tests.Builders;
+using NUnit.Framework;
+
+namespace NTestDataBuilder.Tests
+{
+    class AsProxyTests
+    {
+        [Test]
+        public void GivenBuilderIsSetAsProxy_WhenBuilding_AnNSubstituteProxyIsReturned()
+        {
+            var builder = new CustomerBuilder().AsProxy();
+
+            var proxy = builder.Build();
+
+            proxy.CustomerForHowManyYears(Arg.Any<DateTime>()).Returns(100);
+            Assert.That(proxy.CustomerForHowManyYears(DateTime.Now), Is.EqualTo(100));
+        }
+
+        [Test]
+        public void GivenBuilderThatAltersProxyIsSetAsProxy_WhenBuilding_TheProxyIsAltered()
+        {
+            var builder = new ProxyAlteringCustomerBuilder().AsProxy();
+
+            var proxy = builder.Build();
+
+            Assert.That(proxy.CustomerForHowManyYears(DateTime.Now), Is.EqualTo(ProxyAlteringCustomerBuilder.MemberFor));
+        }
+    }
+}

NTestDataBuilder.Tests/Builders/BasicCustomerBuilder.cs

@@ -4,7 +4,7 @@ namespace NTestDataBuilder.Tests.Builders
 {
     class BasicCustomerBuilder : DataBuilder<Customer, BasicCustomerBuilder>
     {
-        public override Customer Build()
+        protected override Customer BuildObject()
         {
             return new Customer("First Name", "Last Name", 2013);
         }

NTestDataBuilder.Tests/Builders/CustomerBuilder.cs

@@ -44,7 +44,7 @@ public CustomerBuilder WhoJoinedIn(int yearJoined)
             return this;
         }
 
-        public override Customer Build()
+        protected override Customer BuildObject()
         {
             return new Customer(
                 Get(x => x.FirstName),

NTestDataBuilder.Tests/Builders/ProxyAlteringCustomerBuilder.cs

@@ -0,0 +1,21 @@
+using System;
+using NSubstitute;
+using NTestDataBuilder.Tests.Entities;
+
+namespace NTestDataBuilder.Tests.Builders
+{
+    class ProxyAlteringCustomerBuilder : DataBuilder<Customer, ProxyAlteringCustomerBuilder>
+    {
+        public const int MemberFor = 4;
+
+        protected override void AlterProxy(Customer proxy)
+        {
+            proxy.CustomerForHowManyYears(Arg.Any<DateTime>()).Returns(MemberFor);
+        }
+
+        protected override Customer BuildObject()
+        {
+            throw new NotImplementedException();
+        }
+    }
+}

NTestDataBuilder.Tests/Entities/Customer.cs

@@ -18,7 +18,7 @@ public Customer(string firstName, string lastName, int yearJoined)
             YearJoined = yearJoined;
         }
 
-        public int CustomerForHowManyYears(DateTime since)
+        public virtual int CustomerForHowManyYears(DateTime since)
         {
             if (since.Year < YearJoined)
                 throw new ArgumentException("Date must be on year or after year that customer joined.", "since");

NTestDataBuilder.Tests/NTestDataBuilder.Tests.csproj

@@ -47,9 +47,11 @@
     <Reference Include="Microsoft.CSharp" />
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="AsProxyTests.cs" />
     <Compile Include="BuildDataListTests.cs" />
     <Compile Include="Builders\BasicCustomerBuilder.cs" />
     <Compile Include="Builders\CustomerBuilder.cs" />
+    <Compile Include="Builders\ProxyAlteringCustomerBuilder.cs" />
     <Compile Include="BuildTests.cs" />
     <Compile Include="CreateListTests.cs" />
     <Compile Include="Entities\Customer.cs" />

NTestDataBuilder/DataBuilder.cs

@@ -28,13 +28,47 @@ public abstract class DataBuilder<TEntity, TBuilder> : IDataBuilder<TEntity>
         where TBuilder : class, IDataBuilder<TEntity>
     {
         private readonly Dictionary<string, object> _properties = new Dictionary<string, object>();
+        private ProxyBuilder<TEntity> _proxyBuilder;
 
         /// <summary>
         /// Build the object.
         /// </summary>
         /// <returns>The built object</returns>
-        public abstract TEntity Build();
+        public TEntity Build()
+        {
+            if (_proxyBuilder != null)
+            {
+                var proxy = _proxyBuilder.Build();
+                AlterProxy(proxy);
+                return proxy;
+            }
+
+            return BuildObject();
+        }
+
+        /// <summary>
+        /// Build the actual object
+        /// </summary>
+        /// <returns>The built object</returns>
+        protected abstract TEntity BuildObject();
 
+        /// <summary>
+        /// Return an NSubstitute proxy object when .Build() is called rather than a real object.
+        /// </summary>
+        /// <returns>The builder so that other method calls can be chained</returns>
+        public TBuilder AsProxy()
+        {
+            _proxyBuilder = new ProxyBuilder<TEntity>(_properties);
+            return this as TBuilder;
+        }
+
+        /// <summary>
+        /// Alter the proxy object just after it has been built and before it's returned from .Build().
+        /// This allows you to add any .Returns() values that are more complex than the public properties that are proxied by default.
+        /// </summary>
+        /// <param name="proxy">The proxy object</param>
+        protected virtual void AlterProxy(TEntity proxy) {}
+        
         /// <summary>
         /// Records the given value for the given property from <see cref="TEntity"/>.
         /// </summary>