Update tests/CustomIoCTests.cs.

tests/CustomIoCTests.cs

@@ -0,0 +1,35 @@
+using Xunit;
+using Microsoft.Extensions.DependencyInjection;
+
+public class CustomIoCTests
+{
+    [Fact]
+    public void TestTransientRegistration()
+    {
+        var services = new ServiceCollection();
+        var builder = new CustomContainerBuilder();
+        builder.RegisterTransient<IService, ServiceImplementation>();
+        builder.Populate(services);
+        var provider = builder.BuildServiceProvider();
+
+        var service1 = provider.GetService<IService>();
+        var service2 = provider.GetService<IService>();
+
+        Assert.NotSame(service1, service2);
+    }
+
+    [Fact]
+    public void TestSingletonRegistration()
+    {
+        var services = new ServiceCollection();
+        var builder = new CustomContainerBuilder();
+        builder.RegisterSingleton<IService, ServiceImplementation>();
+        builder.Populate(services);
+        var provider = builder.BuildServiceProvider();
+
+        var service1 = provider.GetService<IService>();
+        var service2 = provider.GetService<IService>();
+
+        Assert.Same(service1, service2);
+    }
+}