WeakSingletonTests.cs

using System;
using NUnit.Framework;

namespace Simplify.System.Tests;

[TestFixture]
public class WeakSingletonTests
{
	[Test]
	public void GetInstance_ExplicitTypeBuilder_CreatesInstanceWithTypeBuilder()
	{
		// Arrange

		var singleton = new WeakSingleton<string>(() => new string("Hello"));
		string str = null!;

		// Act & Assert

		Assert.That(() => str = singleton.Instance, Throws.Nothing);
		Assert.That(str, Is.Not.Null);
		Assert.That(str, Is.EqualTo("Hello"));
	}

	[Test]
	public void GetInstance_NullTypeBuilder_CreatesInstanceWithDefaultConstructor()
	{
		// Arrange

		var singleton = new WeakSingleton<object>();
		object obj = null!;

		// Act & Assert

		Assert.That(() => obj = singleton.Instance, Throws.Nothing);
		Assert.That(obj, Is.Not.Null);
	}

#if RELEASE

		[Test]
		public void GetInstanceMultipleTimes_GcCollectBetween_CreatesDifferentInstances()
		{
			// Arrange

			var singleton = new WeakSingleton<TestClass>();
			var obj = singleton.Instance;
			obj.Value = "Some string";

			// Set strong reference to null and allow GC to collect unreferenced object
			obj = null;
			GC.Collect(GC.MaxGeneration, GCCollectionMode.Forced);
			GC.WaitForPendingFinalizers();

			obj = singleton.Instance;

			// Act & Assert

			Assert.That(obj, Is.Not.Null);
			Assert.That(obj.Value, Is.EqualTo("Default"));
		}

#endif

	[OneTimeSetUp]
	public void OneTimeSetUp()
	{
		GC.Collect();
	}

	private class TestClass
	{
		public string Value = "Default";
	}
}