Fix unit tests

Author: JosueNina

Tests/Algorithm/AlgorithmAddSecurityTests.cs

@@ -576,14 +576,7 @@ def set_brokerage_model(algorithm):
             // All models should've been set my the TestBrokerageModel, except the fill model,
             // which should have been set by the TestCustomSecurityInitializer, because user defined
             // initializer should run after the brokerage model initializer
-            if (language == Language.CSharp)
-            {
-                Assert.IsInstanceOf<TestCustomSecurityInitializer.TestFillModel>(security.FillModel);
-            }
-            else
-            {
-                Assert.IsInstanceOf<FillModelPythonWrapper>(security.FillModel);
-            }
+            Assert.IsInstanceOf<TestCustomSecurityInitializer.TestFillModel>(security.FillModel);
         }
 
         public class TestCustomSecurityInitializer : ISecurityInitializer

Tests/Python/SecurityCustomModelTests.cs

@@ -25,6 +25,7 @@
 using QuantConnect.Tests.Common.Securities;
 using System;
 using QuantConnect.Tests.Engine.DataFeeds;
+using System.Reflection;
 
 namespace QuantConnect.Tests.Python
 {
@@ -70,7 +71,7 @@ public void SetBuyingPowerModelFails()
             var code = CreateCustomBuyingPowerModelCode();
             code = code.Replace("GetMaximumOrderQuantityForDeltaBuyingPower", "AnotherName");
             var pyObject = CreateCustomBuyingPowerModel(code);
-            Assert.Throws<NotImplementedException>(() => spy.SetBuyingPowerModel(pyObject));
+            Assert.Throws<TargetInvocationException>(() => spy.SetBuyingPowerModel(pyObject));
         }
 
         private PyObject CreateCustomBuyingPowerModel(string code)