Test completeness

lib/trends/rma/Rma.Tests.cs

@@ -202,4 +202,14 @@ public class RmaTests
         // Result should be finite (not NaN)
         Assert.True(double.IsFinite(resultAfterNaN.Value));
     }
+
+    [Fact]
+    public void Chainability_Works()
+    {
+        var source = new TSeries();
+        var rma = new Rma(source, 10);
+        
+        source.Add(new TValue(DateTime.UtcNow, 100));
+        Assert.Equal(100, rma.Last.Value, 1e-9);
+    }
 }