Implement System.IServiceProvider in AutoMocker. (#128)

* #127 - Implement `System.IServiceProvider` in `AutoMocker`.

* Add tests

Co-authored-by: Kevin B <Keboo@users.noreply.github.com>

Moq.AutoMock.Tests/DescribeGetMock.cs

@@ -65,5 +65,22 @@ public void It_allows_getting_mocked_object_when_overriden()
             Assert.IsNotNull(@protected);
             Assert.IsInstanceOfType(@protected, typeof(ProtectedConstructor1));
         }
+
+        [TestMethod]
+        public void It_gets_mocked_object_via_iserviceprovider()
+        {
+            IServiceProvider mocker = new AutoMocker();
+            var service = mocker.GetService(typeof(Empty));
+            Assert.IsNotNull(service);
+            Assert.IsInstanceOfType(service, typeof(Empty));
+        }
+
+        [TestMethod]
+        public void It_returns_null_for_unmockable_object_via_iserviceprovider()
+        {
+            IServiceProvider mocker = new AutoMocker();
+            var service = mocker.GetService(typeof(string));
+            Assert.IsNull(service);
+        }
     }
 }

Moq.AutoMock/AutoMocker.cs

@@ -18,7 +18,7 @@ namespace Moq.AutoMock
     /// <summary>
     /// An auto-mocking IoC container that generates mock objects using Moq.
     /// </summary>
-    public partial class AutoMocker
+    public partial class AutoMocker : IServiceProvider
     {
         /// <summary>
         /// Initializes an instance of AutoMockers.
@@ -441,6 +441,14 @@ internal bool TryGet(
             return false;
         }
 
+        /// <inheritdoc />
+        object? IServiceProvider.GetService(Type serviceType)
+        {
+            return TryGet(serviceType, new ObjectGraphContext(false), out IInstance? service)
+                ? service.Value
+                : null;
+        }
+
         #endregion Get
 
         #region GetMock