feat: implement SuperTrend indicator with tests and documentation

lib/trends/super/Super.Validation.Tests.cs

@@ -0,0 +1,80 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Skender.Stock.Indicators;
+using Xunit;
+using QuanTAlib.Tests;
+
+namespace QuanTAlib;
+
+public class SuperValidationTests : IDisposable
+{
+    private readonly ValidationTestData _data;
+
+    public SuperValidationTests()
+    {
+        _data = new ValidationTestData();
+    }
+
+    public void Dispose()
+    {
+        Dispose(true);
+        GC.SuppressFinalize(this);
+    }
+
+    protected virtual void Dispose(bool disposing)
+    {
+        if (disposing)
+        {
+            _data.Dispose();
+        }
+    }
+
+    [Fact]
+    public void MatchesSkender()
+    {
+        var super = new Super(10, 3.0);
+        var results = new List<double>();
+        var upper = new List<double>();
+        var lower = new List<double>();
+
+        for (int i = 0; i < _data.Bars.Count; i++)
+        {
+            var res = super.Update(_data.Bars[i]);
+            results.Add(res.Value);
+            upper.Add(super.UpperBand.Value);
+            lower.Add(super.LowerBand.Value);
+        }
+
+        // Skender uses GetSuperTrend
+        var skenderResults = _data.SkenderQuotes.GetSuperTrend(10, 3.0).ToList();
+
+        Assert.Equal(_data.Bars.Count, skenderResults.Count);
+
+        for (int i = 0; i < _data.Bars.Count; i++)
+        {
+            // Skender returns null for warmup
+            if (skenderResults[i].SuperTrend == null)
+            {
+                Assert.True(double.IsNaN(results[i]));
+                continue;
+            }
+
+            Assert.Equal((double)skenderResults[i].SuperTrend!, results[i], 1e-7);
+
+            if (skenderResults[i].UpperBand != null)
+            {
+                Assert.Equal((double)skenderResults[i].UpperBand!, upper[i], 1e-7);
+            }
+
+            if (skenderResults[i].LowerBand != null)
+            {
+                Assert.Equal((double)skenderResults[i].LowerBand!, lower[i], 1e-7);
+            }
+        }
+    }
+
+    // Note: OoplesFinance implementation of SuperTrend diverges significantly from Skender and QuanTAlib.
+    // This is likely due to different initialization logic for ATR or the SuperTrend state itself.
+    // Therefore, we do not validate against Ooples for SuperTrend.
+}