Fixed instruction boundary detection for the specific sequence at address 0x00001874

X86DisassemblerTests/HandlerSelectionTests.cs

@@ -0,0 +1,79 @@
+namespace X86DisassemblerTests;
+
+using System;
+using Xunit;
+using X86Disassembler.X86;
+using X86Disassembler.X86.Handlers;
+using X86Disassembler.X86.Handlers.ArithmeticImmediate;
+using X86Disassembler.X86.Handlers.Inc;
+
+/// <summary>
+/// Tests for handler selection in the InstructionHandlerFactory
+/// </summary>
+public class HandlerSelectionTests
+{
+    /// <summary>
+    /// Tests that the Group1SignExtendedHandler is selected for the 0x83 opcode
+    /// </summary>
+    [Fact]
+    public void InstructionHandlerFactory_SelectsGroup1SignExtendedHandler_For0x83Opcode()
+    {
+        // Arrange
+        byte[] codeBuffer = new byte[] { 0x83, 0xC1, 0x04 }; // ADD ecx, 0x04
+        var decoder = new InstructionDecoder(codeBuffer, codeBuffer.Length);
+        var factory = new InstructionHandlerFactory(codeBuffer, decoder, codeBuffer.Length);
+        
+        // Act
+        var handler = factory.GetHandler(0x83);
+        
+        // Assert
+        Assert.NotNull(handler);
+        Assert.IsType<Group1SignExtendedHandler>(handler);
+    }
+    
+    /// <summary>
+    /// Tests that the IncRegHandler is NOT selected for the 0x83 opcode
+    /// </summary>
+    [Fact]
+    public void InstructionHandlerFactory_DoesNotSelectIncRegHandler_For0x83Opcode()
+    {
+        // Arrange
+        byte[] codeBuffer = new byte[] { 0x83, 0xC1, 0x04 }; // ADD ecx, 0x04
+        var decoder = new InstructionDecoder(codeBuffer, codeBuffer.Length);
+        var factory = new InstructionHandlerFactory(codeBuffer, decoder, codeBuffer.Length);
+        
+        // Act
+        var handler = factory.GetHandler(0x83);
+        
+        // Assert
+        Assert.NotNull(handler);
+        Assert.IsNotType<IncRegHandler>(handler);
+    }
+    
+    /// <summary>
+    /// Tests the specific problematic sequence
+    /// </summary>
+    [Fact]
+    public void InstructionHandlerFactory_HandlesProblematicSequence_Correctly()
+    {
+        // Arrange - This is the sequence from the problematic example
+        byte[] codeBuffer = new byte[] { 0x08, 0x83, 0xC1, 0x04, 0x50, 0xE8, 0x42, 0x01, 0x00, 0x00 };
+        var disassembler = new Disassembler(codeBuffer, 0);
+        
+        // Act - Disassemble the entire sequence
+        var instructions = disassembler.Disassemble();
+        
+        // Assert - We should have at least 3 instructions
+        Assert.True(instructions.Count >= 3, $"Expected at least 3 instructions, but got {instructions.Count}");
+        
+        // First instruction should be OR
+        Assert.Equal("or", instructions[0].Mnemonic);
+        
+        // Second instruction should be ADD ecx, imm8
+        Assert.Equal("add", instructions[1].Mnemonic);
+        Assert.Contains("ecx", instructions[1].Operands);
+        
+        // Third instruction should be PUSH eax
+        Assert.Equal("push", instructions[2].Mnemonic);
+    }
+}