Added unit testing

Syrette.Tests/ServiceContainerConstructorSelectionTests.cs

@@ -0,0 +1,127 @@
+namespace Syrette.Tests;
+
+public class ServiceContainerConstructorSelectionTests
+{
+    public class CtorWithOptional
+    {
+        public ITestService? A { get; }
+        public string? Name { get; }
+
+        public CtorWithOptional(ITestService a, string? name = "default")
+        {
+            A = a;
+            Name = name;
+        }
+    }
+
+    public class CtorWithExactMatch
+    {
+        public int Value { get; }
+
+        public CtorWithExactMatch(int value) { Value = value; }
+        public CtorWithExactMatch(int value, string label) { Value = value; }
+    }
+
+    public class NoSatisfiableCtor
+    {
+        public NoSatisfiableCtor(int value) { }
+    }
+
+    [Fact]
+    public void Greedy_picks_most_satisfiable_constructor()
+    {
+        var container = new ServiceContainer();
+        container.AddSingleton<ITestService, TestServiceImpl>();
+        container.AddSingleton<ITestServiceB, TestServiceBImpl>();
+
+        container.AddSingleton<TestMultiCtor>();
+        var instance = container.GetService<TestMultiCtor>();
+
+        Assert.NotNull(instance.A);
+        Assert.NotNull(instance.B);
+        Assert.Null(instance.C);
+    }
+
+    [Fact]
+    public void Greedy_picks_all_satisfied_over_partial()
+    {
+        var container = new ServiceContainer();
+        container.AddSingleton<ITestService, TestServiceImpl>();
+        container.AddSingleton<ITestServiceB, TestServiceBImpl>();
+        container.AddSingleton<ITestServiceC, TestServiceCImpl>();
+
+        container.AddSingleton<TestMultiCtor>();
+        var instance = container.GetService<TestMultiCtor>();
+
+        Assert.NotNull(instance.A);
+        Assert.NotNull(instance.B);
+        Assert.NotNull(instance.C);
+    }
+
+    [Fact]
+    public void Greedy_falls_back_to_1_param_when_only_1_satisfiable()
+    {
+        var container = new ServiceContainer();
+        container.AddSingleton<ITestService, TestServiceImpl>();
+
+        container.AddSingleton<TestMultiCtor>();
+        var instance = container.GetService<TestMultiCtor>();
+
+        Assert.NotNull(instance.A);
+        Assert.Null(instance.B);
+        Assert.Null(instance.C);
+    }
+
+    [Fact]
+    public void Optional_parameter_used_when_not_registered()
+    {
+        var container = new ServiceContainer();
+        container.AddSingleton<ITestService, TestServiceImpl>();
+        container.AddSingleton<CtorWithOptional>();
+
+        var instance = container.GetService<CtorWithOptional>();
+        Assert.NotNull(instance.A);
+        Assert.Equal("default", instance.Name);
+    }
+
+    [Fact]
+    public void Registration_args_satisfy_constructor()
+    {
+        var container = new ServiceContainer();
+        container.AddSingleton<CtorWithExactMatch, CtorWithExactMatch>(42);
+
+        var instance = container.GetService<CtorWithExactMatch>();
+        Assert.Equal(42, instance.Value);
+    }
+
+    [Fact]
+    public void Resolution_args_satisfy_constructor()
+    {
+        var container = new ServiceContainer();
+        container.AddSingleton<CtorWithExactMatch, CtorWithExactMatch>();
+
+        var instance = (CtorWithExactMatch)container.GetService(
+            typeof(CtorWithExactMatch), new object[] { 99 });
+        Assert.Equal(99, instance.Value);
+    }
+
+    [Fact]
+    public void Resolution_args_override_registration_args()
+    {
+        var container = new ServiceContainer();
+        container.AddSingleton<CtorWithExactMatch, CtorWithExactMatch>(10);
+
+        var instance = (CtorWithExactMatch)container.GetService(
+            typeof(CtorWithExactMatch), new object[] { 20 });
+        Assert.Equal(20, instance.Value);
+    }
+
+    [Fact]
+    public void No_suitable_constructor_throws()
+    {
+        var container = new ServiceContainer();
+        container.AddSingleton<NoSatisfiableCtor>();
+        Assert.Throws<InvalidOperationException>(() =>
+            container.GetService<NoSatisfiableCtor>());
+    }
+}