Add support for TUnit Class Constructors (#1362)

Author: SimonCropp

src/Directory.Packages.props

@@ -16,6 +16,7 @@
     <PackageVersion Include="Microsoft.Bcl.AsyncInterfaces" Version="9.0.0" />
     <PackageVersion Include="Microsoft.CodeAnalysis.Analyzers" Version="3.3.4" />
     <PackageVersion Include="Microsoft.CodeAnalysis.CSharp" Version="4.9.2" />
+    <PackageVersion Include="Microsoft.Extensions.DependencyInjection" Version="9.0.0" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
     <PackageVersion Include="NUnit" Version="4.2.2" />
     <PackageVersion Include="MSTest" Version="3.6.3" />

src/Verify.TUnit.Tests/ClassConstructor/ClassConstructor.cs

@@ -0,0 +1,21 @@
+using Microsoft.Extensions.DependencyInjection;
+using TUnit.Core.Interfaces;
+
+public class ClassConstructor : IClassConstructor
+{
+    static readonly IServiceProvider serviceProvider = CreateServiceProvider();
+
+    AsyncServiceScope scope;
+
+    public T Create<[DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicConstructors)] T>(ClassConstructorMetadata classConstructorMetadata)
+        where T : class
+    {
+        scope = serviceProvider.CreateAsyncScope();
+        return ActivatorUtilities.GetServiceOrCreateInstance<T>(scope.ServiceProvider);
+    }
+
+    static IServiceProvider CreateServiceProvider() =>
+        new ServiceCollection()
+            .AddSingleton<string>("SingletonValue")
+            .BuildServiceProvider();
+}

src/Verify.TUnit.Tests/ClassConstructor/ClassConstructorMixedWithArgumentTests.Test.verified.txt

@@ -0,0 +1 @@
+SingletonValue

src/Verify.TUnit.Tests/ClassConstructor/ClassConstructorMixedWithArgumentTests.Test_service=2.verified.txt

@@ -0,0 +1 @@
+2

src/Verify.TUnit.Tests/ClassConstructor/ClassConstructorMixedWithArgumentTests.cs

@@ -0,0 +1,11 @@
+[ClassConstructor<ClassConstructor>]
+[Arguments("2")]
+public class ClassConstructorMixedWithArgumentTests(string service)
+{
+    [Test]
+    public async Task Test()
+    {
+        await Assert.That(service).IsNotNull();
+        await Verify(service);
+    }
+}

src/Verify.TUnit.Tests/ClassConstructor/ClassConstructorTests.Test.verified.txt

@@ -0,0 +1 @@
+SingletonValue

src/Verify.TUnit.Tests/ClassConstructor/ClassConstructorTests.cs

@@ -0,0 +1,10 @@
+[ClassConstructor<ClassConstructor>]
+public class ClassConstructorTests(string service)
+{
+    [Test]
+    public async Task Test()
+    {
+        await Assert.That(service).IsNotNull();
+        await Verify(service);
+    }
+}

src/Verify.TUnit.Tests/Verify.TUnit.Tests.csproj

@@ -10,6 +10,7 @@
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection" />
     <PackageReference Include="ProjectDefaults" PrivateAssets="all" />
 
     <ProjectReference Include="..\TargetLibrary\TargetLibrary.csproj" />

src/Verify.TUnit/TUnitExtensions.cs

@@ -4,51 +4,34 @@ static class TUnitExtensions
     {
         var methodParameterNames = details.MethodInfo.ParameterNames();
 
-        var names = GetConstructorParameterNames(details.ClassType, details.TestClassArguments.Length)
-            .ToList();
+        var constructorParameterNames = GetConstructorParameterNames(details);
         if (methodParameterNames == null)
         {
-            if (names.Count == 0)
+            if (constructorParameterNames.Count == 0)
             {
                 return null;
             }
 
-            return names;
+            return constructorParameterNames;
         }
 
-        if (names.Count == 0 &&
-             methodParameterNames.Count == 0)
+        if (constructorParameterNames.Count == 0 &&
+            methodParameterNames.Count == 0)
         {
             return null;
         }
 
-        return [.. names, .. methodParameterNames];
+        return [.. constructorParameterNames, .. methodParameterNames];
     }
 
-    public static IEnumerable<string> GetConstructorParameterNames(this Type type, int argumentsLength)
+    static List<string> GetConstructorParameterNames(TestDetails details)
     {
-        IEnumerable<string>? names = null;
-        foreach (var constructor in type.GetConstructors(BindingFlags.Instance | BindingFlags.Public))
+        var constructors = details.ClassType.GetConstructors(BindingFlags.Instance | BindingFlags.Public);
+        if (constructors.Length <= 1)
         {
-            var parameters = constructor.GetParameters();
-            if (parameters.Length != argumentsLength)
-            {
-                continue;
-            }
-
-            if (names != null)
-            {
-                throw new($"Found multiple constructors with {argumentsLength} parameters. Unable to derive names of parameters. Instead use UseParameters to pass in explicit parameter.");
-            }
-
-            names = parameters.Select(_ => _.Name!);
-        }
-
-        if (names == null)
-        {
-            throw new($"Could not find constructor with {argumentsLength} parameters.");
+            return constructors[0].GetParameters().Select(_ => _.Name!).ToList();
         }
 
-        return names;
+        throw new("Found multiple constructors. Unable to derive names of parameters. Instead use UseParameters to pass in explicit parameter.");
     }
-}
+}