QuanTAlib/lib/oscillators/stoch/Stoch.Validation.Tests.cs

using Skender.Stock.Indicators;
using Xunit;

namespace QuanTAlib.Tests;

/// <summary>
/// Stochastic Oscillator validation tests.
/// Cross-validates against Skender.Stock.Indicators.GetStoch with smoothPeriods=1
/// (Fast Stochastic matches our raw %K), plus self-consistency checks.
/// </summary>
public sealed class StochValidationTests : IDisposable
{
    private readonly ValidationTestData _data = new();
    private bool _disposed;

    public void Dispose()
    {
        Dispose(disposing: true);
        GC.SuppressFinalize(this);
    }

    private void Dispose(bool disposing)
    {
        if (!_disposed && disposing)
        {
            _data.Dispose();
            _disposed = true;
        }
    }

    private static TBarSeries GenerateSeries(int count, int seed = 42)
    {
        var gbm = new GBM(startPrice: 100.0, mu: 0.02, sigma: 0.15, seed: seed);
        return gbm.Fetch(count, DateTime.UtcNow.Ticks, TimeSpan.FromMinutes(1));
    }

    // --- A) Streaming vs Batch agreement ---

    [Fact]
    public void Streaming_Matches_Batch()
    {
        var series = GenerateSeries(300);
        const int kLength = 14;
        const int dPeriod = 3;

        var stoch = new Stoch(kLength, dPeriod);
        for (int i = 0; i < series.Count; i++)
        {
            stoch.Update(series[i]);
        }

        var (batchK, batchD) = Stoch.Batch(series, kLength, dPeriod);

        Assert.Equal(stoch.K.Value, batchK[^1].Value, 1e-6);
        Assert.Equal(stoch.D.Value, batchD[^1].Value, 1e-6);
    }

    // --- B) Span matches TBarSeries ---

    [Fact]
    public void Span_Matches_TBarSeries()
    {
        var series = GenerateSeries(200);
        const int kLength = 14;
        const int dPeriod = 3;

        var (tbK, tbD) = Stoch.Batch(series, kLength, dPeriod);

        var kOut = new double[series.Count];
        var dOut = new double[series.Count];
        Stoch.Batch(series.HighValues, series.LowValues, series.CloseValues,
            kOut.AsSpan(), dOut.AsSpan(), kLength, dPeriod);

        for (int i = 0; i < series.Count; i++)
        {
            Assert.Equal(tbK.Values[i], kOut[i], 12);
            Assert.Equal(tbD.Values[i], dOut[i], 12);
        }
    }

    // --- C) Constant bars → K=0 ---

    [Fact]
    public void ConstantBars_K_Is_Zero()
    {
        const int kLength = 14;
        const int dPeriod = 3;
        int count = 50;

        var bars = new TBarSeries();
        for (int i = 0; i < count; i++)
        {
            bars.Add(new TBar(DateTime.UtcNow.AddMinutes(i), 50, 50, 50, 50, 100));
        }

        var (kSeries, dSeries) = Stoch.Batch(bars, kLength, dPeriod);

        // When range=0 for all bars, %K and %D should be 0
        for (int i = kLength - 1; i < count; i++)
        {
            Assert.Equal(0.0, kSeries.Values[i], 1e-10);
            Assert.Equal(0.0, dSeries.Values[i], 1e-10);
        }
    }

    // --- D) Directional correctness ---

    [Fact]
    public void Rising_Produces_High_K()
    {
        const int kLength = 5;
        const int dPeriod = 3;

        var bars = new TBarSeries();
        for (int i = 0; i < 20; i++)
        {
            double price = 100.0 + (i * 2.0);
            bars.Add(new TBar(DateTime.UtcNow.AddMinutes(i), price, price + 1, price - 1, price + 1, 100));
        }

        var stoch = new Stoch(kLength, dPeriod);
        for (int i = 0; i < bars.Count; i++)
        {
            stoch.Update(bars[i]);
        }

        // Close at recent high → %K should be near 100
        Assert.True(stoch.K.Value > 80.0);
    }

    [Fact]
    public void Falling_Produces_Low_K()
    {
        const int kLength = 5;
        const int dPeriod = 3;

        var bars = new TBarSeries();
        for (int i = 0; i < 20; i++)
        {
            double price = 200.0 - (i * 2.0);
            bars.Add(new TBar(DateTime.UtcNow.AddMinutes(i), price, price + 1, price - 1, price - 1, 100));
        }

        var stoch = new Stoch(kLength, dPeriod);
        for (int i = 0; i < bars.Count; i++)
        {
            stoch.Update(bars[i]);
        }

        // Close at recent low → %K should be near 0
        Assert.True(stoch.K.Value < 20.0);
    }

    // --- E) Cross-validation with Skender ---

    [Fact]
    public void Skender_K_Matches_With_SmoothK1()
    {
        // Skender GetStoch(lookbackPeriods, signalPeriods, smoothPeriods)
        // smoothPeriods=1 means no SMA smoothing on %K → raw Fast %K == our %K
        const int kLength = 14;
        const int dPeriod = 3;

        var (qK, qD) = Stoch.Batch(_data.Bars, kLength, dPeriod);

        var skResults = _data.SkenderQuotes.GetStoch(kLength, dPeriod, 1).ToList();

        // Compare converged values (skip warmup)
        int start = kLength + dPeriod;
        int totalCompared = 0;
        int mismatches = 0;

        for (int i = start; i < _data.Bars.Count; i++)
        {
            double? skK = skResults[i].Oscillator;
            double? skD = skResults[i].Signal;

            if (skK.HasValue && skD.HasValue)
            {
                totalCompared++;
                double errK = Math.Abs(qK.Values[i] - skK.Value);
                double errD = Math.Abs(qD.Values[i] - skD.Value);

                if (errK > 1e-6 || errD > 1e-6)
                {
                    mismatches++;
                }
            }
        }

        // Allow small fraction of mismatches due to warmup initialization differences
        Assert.True(totalCompared > 0, "No Skender results to compare");
        double mismatchRate = (double)mismatches / totalCompared;
        Assert.True(mismatchRate < 0.05, $"Mismatch rate {mismatchRate:P2} exceeds 5% threshold ({mismatches}/{totalCompared})");
    }

    // --- F) Determinism ---

    [Fact]
    public void Deterministic_Across_Runs()
    {
        var series = GenerateSeries(200, seed: 99);
        const int kLength = 14;
        const int dPeriod = 3;

        var (k1, d1) = Stoch.Batch(series, kLength, dPeriod);
        var (k2, d2) = Stoch.Batch(series, kLength, dPeriod);

        for (int i = 0; i < series.Count; i++)
        {
            Assert.Equal(k1.Values[i], k2.Values[i], 15);
            Assert.Equal(d1.Values[i], d2.Values[i], 15);
        }
    }

    // --- G) Multi-period consistency ---

    [Fact]
    public void Different_Periods_Produce_Different_Results()
    {
        var series = GenerateSeries(100);

        var (k5, _) = Stoch.Batch(series, kLength: 5, dPeriod: 3);
        var (k20, _) = Stoch.Batch(series, kLength: 20, dPeriod: 3);

        // Different kLength should produce different %K values after warmup
        bool anyDifferent = false;
        for (int i = 20; i < 100; i++)
        {
            if (Math.Abs(k5.Values[i] - k20.Values[i]) > 0.01)
            {
                anyDifferent = true;
                break;
            }
        }
        Assert.True(anyDifferent);
    }

    // --- H) Calculate returns both results and indicator ---

    [Fact]
    public void Calculate_Produces_Consistent_Results()
    {
        var series = GenerateSeries(100);
        const int kLength = 14;
        const int dPeriod = 3;

        var (results, indicator) = Stoch.Calculate(series, kLength, dPeriod);

        Assert.Equal(100, results.K.Count);
        Assert.Equal(100, results.D.Count);
        Assert.True(indicator.IsHot);
        Assert.True(double.IsFinite(indicator.K.Value));
        Assert.True(double.IsFinite(indicator.D.Value));
    }
}