Add test file just to be sure

src/BizHawk.Tests/Common/ConversionTests.cs

@@ -0,0 +1,40 @@
+using System;
+using System.Buffers.Binary;
+using System.Runtime.CompilerServices;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace BizHawk.Tests.Common;
+
+// test for RamSearchEngine.ReinterpretAsF32
+[TestClass]
+public class ConversionTests
+{
+	private static float ReinterpretAsF32Unsafe(long l)
+	{
+		return Unsafe.As<long, float>(ref l);
+	}
+
+	private static readonly byte[] ScratchSpace = new byte[8];
+
+	private static float ReinterpretAsF32BitConverter(long l)
+	{
+		BinaryPrimitives.WriteInt64LittleEndian(ScratchSpace, l);
+		return BitConverter.ToSingle(ScratchSpace, startIndex: 0);
+	}
+
+	[TestMethod]
+	[DataRow(0, 0)]
+	[DataRow(1, 1.401298E-45F)]
+	[DataRow(1109917696, 42)]
+	[DataRow(1123477881, 123.456F)]
+	[DataRow(3212836864, -1)]
+	[DataRow(0x7fffffffbf800000, -1)]
+	public void TestReinterpretAsF32(long input, float expected)
+	{
+		float f32BitConverter = ReinterpretAsF32BitConverter(input);
+		float f32Unsafe = ReinterpretAsF32Unsafe(input);
+
+		Assert.AreEqual(expected, f32BitConverter);
+		Assert.AreEqual(expected, f32Unsafe);
+	}
+}