#if DEBUG private static #else private const (dotnet#96538)

Author: kzrnm

src/libraries/System.Runtime.Numerics/src/System/Number.BigInteger.cs

@@ -657,7 +657,13 @@ internal static ParsingStatus TryParseBigIntegerBinaryNumberStyle(ReadOnlySpan<c
         // algorithm with a running time of O(N^2). And if it is greater than the threshold, use
         // a divide-and-conquer algorithm with a running time of O(NlogN).
         //
-        private static int s_naiveThreshold = 20000; // non-readonly for testing
+#if DEBUG
+        // Mutable for unit testing...
+        private static
+#else
+        private const
+#endif
+        int s_naiveThreshold = 20000;
         private static ParsingStatus NumberToBigInteger(ref NumberBuffer number, out BigInteger result)
         {
             int currentBufferSize = 0;