Added unit testing

Syrette.Tests/ServiceContainerRegistrationTests.cs

@@ -0,0 +1,100 @@
+namespace Syrette.Tests;
+
+public class ServiceContainerRegistrationTests
+{
+    [Fact]
+    public void AddSingleton_TInterface_TImplementation_registers_successfully()
+    {
+        var container = new ServiceContainer();
+        container.AddSingleton<ITestService, TestServiceImpl>();
+        Assert.NotNull(container.GetService<ITestService>());
+    }
+
+    [Fact]
+    public void AddSingleton_TInterface_TImplementation_with_args_registers_successfully()
+    {
+        var container = new ServiceContainer();
+        container.AddSingleton<ITestService, TestDeepService>(Guid.NewGuid());
+        Assert.NotNull(container.GetService<ITestService>());
+    }
+
+    [Fact]
+    public void AddSingleton_TClass_registers_successfully()
+    {
+        var container = new ServiceContainer();
+        container.AddSingleton<TestServiceImpl>();
+        Assert.NotNull(container.GetService<TestServiceImpl>());
+    }
+
+    [Fact]
+    public void AddSingleton_TClass_with_args_registers_successfully()
+    {
+        var container = new ServiceContainer();
+        container.AddSingleton<TestDeepService>(Guid.NewGuid());
+        Assert.NotNull(container.GetService<TestDeepService>());
+    }
+
+    [Fact]
+    public void AddTransient_TInterface_TImplementation_registers_successfully()
+    {
+        var container = new ServiceContainer();
+        container.AddTransient<ITestService, TestServiceImpl>();
+        Assert.NotNull(container.GetService<ITestService>());
+    }
+
+    [Fact]
+    public void AddTransient_TInterface_TImplementation_with_args_registers_successfully()
+    {
+        var container = new ServiceContainer();
+        container.AddTransient<ITestService, TestDeepService>(Guid.NewGuid());
+        Assert.NotNull(container.GetService<ITestService>());
+    }
+
+    [Fact]
+    public void AddTransient_TClass_registers_successfully()
+    {
+        var container = new ServiceContainer();
+        container.AddTransient<TestServiceImpl>();
+        Assert.NotNull(container.GetService<TestServiceImpl>());
+    }
+
+    [Fact]
+    public void AddTransient_TClass_with_args_registers_successfully()
+    {
+        var container = new ServiceContainer();
+        container.AddTransient<TestDeepService>(Guid.NewGuid());
+        Assert.NotNull(container.GetService<TestDeepService>());
+    }
+
+    [Fact]
+    public void Fluent_chaining_returns_same_container()
+    {
+        var container = new ServiceContainer();
+        var result = container
+            .AddSingleton<ITestService, TestServiceImpl>()
+            .AddTransient<TestServiceImpl>();
+        Assert.Same(container, result);
+    }
+
+    [Fact]
+    public void Duplicate_registration_same_pair_throws()
+    {
+        var container = new ServiceContainer();
+        container.AddSingleton<ITestService, TestServiceImpl>();
+        Assert.Throws<InvalidOperationException>(() =>
+            container.AddSingleton<ITestService, TestServiceImpl>());
+    }
+
+    [Fact]
+    public void Duplicate_registration_different_impl_for_same_service_allowed()
+    {
+        var container = new ServiceContainer();
+        container.AddSingleton<ITestService, TestServiceImpl>();
+        container.AddSingleton<ITestService, TestServiceAlt>();
+
+        var services = container.GetServiceTypes<ITestService>();
+        Assert.Equal(2, services.Count);
+        Assert.Contains(typeof(TestServiceImpl), services);
+        Assert.Contains(typeof(TestServiceAlt), services);
+    }
+}