name: indicator-buffer description: Implement BufferList incremental indicators with efficient state management. Use for IIncrementFromChain or IIncrementFromQuote implementations. Covers interface selection, constructor patterns, and BufferListTestBase testing requirements.

BufferList indicator development

Interface selection

All BufferList implementations support IQuote inputs from the base class. The interface determines what additional input types are supported:

Constructor pattern

public class MyIndicatorList : BufferList<MyResult>, IIncrementFromChain
{
    private readonly Queue<double> _buffer;

    // Primary constructor (parameters only)
    public MyIndicatorList(int lookbackPeriods)
    {
        ArgumentOutOfRangeException.ThrowIfLessThan(lookbackPeriods, 1);
        LookbackPeriods = lookbackPeriods;
        _buffer = new Queue<double>(lookbackPeriods);
    }

    // Chaining constructor (parameters + quotes)
    public MyIndicatorList(int lookbackPeriods, IReadOnlyList<IQuote> quotes)
        : this(lookbackPeriods) => Add(quotes);
}

Buffer management

Use extension methods from BufferListUtilities:

• _buffer.Update(capacity, value) - Standard rolling buffer
• _buffer.UpdateWithDequeue(capacity, value) - Returns dequeued value for sum adjustment

Note: Future refactor planned to rename BufferListUtilities to BufferListExtensions for .NET idiomatic naming.

State management

Use Clear() to reset all internal state:

public override void Clear()
{
    base.Clear();
    _buffer.Clear();
    _bufferSum = 0;
}

Testing constraints

• Inherit BufferListTestBase (NOT TestBase)
• Implement test interface matching increment interface:
  • IIncrementFromChain → ITestChainBufferList
  • IIncrementFromQuote → ITestQuoteBufferList
• Verify exact Series parity with bufferResults.IsExactly(seriesResults) (NOT Should().Be())
• All 5 base class tests pass (incremental adds, batching, constructor chaining, Clear(), auto-pruning)

Required implementation

• Source code: src/**/{IndicatorName}.BufferList.cs file exists
  • Inherits BufferList<TResult> and implements correct increment interface
  • Two constructors: primary + chaining via : this(...) => Add(quotes);
  • Uses BufferListUtilities.Update() or UpdateWithDequeue()
  • Clear() resets results and all internal buffers
• Unit testing: tests/indicators/**/{IndicatorName}.BufferList.Tests.cs exists
  • Inherits BufferListTestBase and implements correct test interface
  • All 5 required tests from base class pass
  • Verifies equivalence with Series results
• Catalog registration: Registered in Catalog.Listings.cs
• Performance benchmark: Add to #file:../../../tools/performance/Perf.Buffer.cs
• Public documentation: Update docs/indicators/{IndicatorName}.md
• Regression tests: Add to tests/indicators/**/{IndicatorName}.Regression.Tests.cs
• Migration guide: Update docs/migration.md for notable and breaking changes from v2

Common pitfalls

• Manual buffer management instead of using BufferListUtilities extension methods
• Not implementing Clear() to reset all internal state properly
• Using Should().Be() instead of IsExactly() for Series parity verification

Last updated: January 25, 2026