FastRng/FastRngTests/Distributions/StudentTNu1.cs

using System;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using System.Threading.Tasks;
using FastRng;
using NUnit.Framework;

namespace FastRngTests.Distributions;

[ExcludeFromCodeCoverage]
public class StudentTNu1
{
    [Test]
    [Category(TestCategories.COVER)]
    [Category(TestCategories.NORMAL)]
    public void TestStudentTDistribution01()
    {
        using var rng = new MultiThreadedRng<float>();
        var dist = new FastRng.Distributions.StudentTNu1<float>(rng);
        var fra = new FrequencyAnalysis();

        for (var n = 0; n < 100_000; n++)
            fra.CountThis(dist.NextNumber());
            
        var result = fra.NormalizeAndPlotEvents(TestContext.WriteLine);

        Assert.That(result[0], Is.EqualTo(1.000000000f).Within(0.2f));
        Assert.That(result[1], Is.EqualTo(0.999700120f).Within(0.2f));
        Assert.That(result[2], Is.EqualTo(0.999200719f).Within(0.2f));
            
        Assert.That(result[21], Is.EqualTo(0.953929798f).Within(0.2f));
        Assert.That(result[22], Is.EqualTo(0.949852788f).Within(0.2f));
        Assert.That(result[23], Is.EqualTo(0.945631619f).Within(0.2f));
            
        Assert.That(result[50], Is.EqualTo(0.793667169f).Within(0.095f));
            
        Assert.That(result[75], Is.EqualTo(0.633937627f).Within(0.09f));
        Assert.That(result[85], Is.EqualTo(0.574902276f).Within(0.09f));
        Assert.That(result[90], Is.EqualTo(0.547070729f).Within(0.09f));
            
        Assert.That(result[97], Is.EqualTo(0.510150990f).Within(0.09f));
        Assert.That(result[98], Is.EqualTo(0.505075501f).Within(0.09f));
        Assert.That(result[99], Is.EqualTo(0.500050000f).Within(0.09f));
    }
        
    [Test]
    [Category(TestCategories.COVER)]
    [Category(TestCategories.NORMAL)]
    public void TestStudentTGeneratorWithRange01()
    {
        using var rng = new MultiThreadedRng<float>();
        var dist = new FastRng.Distributions.StudentTNu1<float>(rng);
        var samples = new float[1_000];
        for (var n = 0; n < samples.Length; n++)
            samples[n] = dist.NextNumber(-1.0f, 1.0f);
            
        Assert.That(samples.Min(), Is.GreaterThanOrEqualTo(-1.0f), "Min out of range");
        Assert.That(samples.Max(), Is.LessThanOrEqualTo(1.0f), "Max out of range");
    }
        
    [Test]
    [Category(TestCategories.COVER)]
    [Category(TestCategories.NORMAL)]
    public void TestStudentTGeneratorWithRange02()
    {
        using var rng = new MultiThreadedRng<float>();
        var dist = new FastRng.Distributions.StudentTNu1<float>(rng);
        var samples = new float[1_000];
        for (var n = 0; n < samples.Length; n++)
            samples[n] = dist.NextNumber(0.0f, 1.0f);
            
        Assert.That(samples.Min(), Is.GreaterThanOrEqualTo(0.0f), "Min is out of range");
        Assert.That(samples.Max(), Is.LessThanOrEqualTo(1.0f), "Max is out of range");
    }

    [Test]
    [Category(TestCategories.COVER)]
    [Category(TestCategories.NORMAL)]
    public void NoRandomNumberGenerator01()
    {
        Assert.Throws<ArgumentNullException>(() => new FastRng.Distributions.StudentTNu1<float>(null));
    }
}