Initial commit.

PerfectNumbers.Core.Tests/MersenneNumberTester/MersenneResidueModeTests.cs

@@ -0,0 +1,16 @@
+using FluentAssertions;
+using Xunit;
+
+namespace PerfectNumbers.Core.Tests;
+
+[Trait("Category", "Fast")]
+public class MersenneResidueModeTests
+{
+    [Fact]
+    public void IsMersennePrime_residue_mode_rejects_composite_exponent()
+    {
+        var tester = new MersenneNumberTester(useResidue: true, useIncremental: false);
+        tester.IsMersennePrime(136_000_002UL).Should().BeFalse();
+    }
+}
+