Added proper REPNE prefix handling and comprehensive string instruction tests

X86DisassemblerTests/StringInstructionHandlerTests.cs

@@ -11,10 +11,10 @@ using X86Disassembler.X86.Handlers.String;
 public class StringInstructionHandlerTests
 {
     /// <summary>
-    /// Tests the RepMovsHandler for decoding REP MOVS instruction
+    /// Tests the StringInstructionHandler for decoding REP MOVS instruction
     /// </summary>
     [Fact]
-    public void RepMovsHandler_DecodesRepMovs_Correctly()
+    public void StringInstructionHandler_DecodesRepMovs_Correctly()
     {
         // Arrange
         // REP MOVS (F3 A5)
@@ -29,4 +29,104 @@ public class StringInstructionHandlerTests
         Assert.Equal("rep movs", instruction.Mnemonic);
         Assert.Equal("dword ptr [edi], dword ptr [esi]", instruction.Operands);
     }
+    
+    /// <summary>
+    /// Tests the StringInstructionHandler for decoding REPNE SCAS instruction
+    /// </summary>
+    [Fact]
+    public void StringInstructionHandler_DecodesRepneScas_Correctly()
+    {
+        // Arrange
+        // REPNE SCAS (F2 AF)
+        byte[] codeBuffer = new byte[] { 0xF2, 0xAF };
+        var decoder = new InstructionDecoder(codeBuffer, codeBuffer.Length);
+        
+        // Act
+        var instruction = decoder.DecodeInstruction();
+        
+        // Assert
+        Assert.NotNull(instruction);
+        Assert.Equal("repne scas", instruction.Mnemonic);
+        Assert.Equal("eax, dword ptr [edi]", instruction.Operands);
+    }
+    
+    /// <summary>
+    /// Tests the StringInstructionHandler for decoding MOVS instruction without prefix
+    /// </summary>
+    [Fact]
+    public void StringInstructionHandler_DecodesMovs_Correctly()
+    {
+        // Arrange
+        // MOVS (A5)
+        byte[] codeBuffer = new byte[] { 0xA5 };
+        var decoder = new InstructionDecoder(codeBuffer, codeBuffer.Length);
+        
+        // Act
+        var instruction = decoder.DecodeInstruction();
+        
+        // Assert
+        Assert.NotNull(instruction);
+        Assert.Equal("movs", instruction.Mnemonic);
+        Assert.Equal("dword ptr [edi], dword ptr [esi]", instruction.Operands);
+    }
+    
+    /// <summary>
+    /// Tests the StringInstructionHandler for decoding STOS instruction without prefix
+    /// </summary>
+    [Fact]
+    public void StringInstructionHandler_DecodesStosb_Correctly()
+    {
+        // Arrange
+        // STOSB (AA)
+        byte[] codeBuffer = new byte[] { 0xAA };
+        var decoder = new InstructionDecoder(codeBuffer, codeBuffer.Length);
+        
+        // Act
+        var instruction = decoder.DecodeInstruction();
+        
+        // Assert
+        Assert.NotNull(instruction);
+        Assert.Equal("stos", instruction.Mnemonic);
+        Assert.Equal("byte ptr [edi], al", instruction.Operands);
+    }
+    
+    /// <summary>
+    /// Tests the StringInstructionHandler for decoding LODS instruction without prefix
+    /// </summary>
+    [Fact]
+    public void StringInstructionHandler_DecodesLodsd_Correctly()
+    {
+        // Arrange
+        // LODSD (AD)
+        byte[] codeBuffer = new byte[] { 0xAD };
+        var decoder = new InstructionDecoder(codeBuffer, codeBuffer.Length);
+        
+        // Act
+        var instruction = decoder.DecodeInstruction();
+        
+        // Assert
+        Assert.NotNull(instruction);
+        Assert.Equal("lods", instruction.Mnemonic);
+        Assert.Equal("eax, dword ptr [esi]", instruction.Operands);
+    }
+    
+    /// <summary>
+    /// Tests the StringInstructionHandler for decoding SCAS instruction without prefix
+    /// </summary>
+    [Fact]
+    public void StringInstructionHandler_DecodesScasb_Correctly()
+    {
+        // Arrange
+        // SCASB (AE)
+        byte[] codeBuffer = new byte[] { 0xAE };
+        var decoder = new InstructionDecoder(codeBuffer, codeBuffer.Length);
+        
+        // Act
+        var instruction = decoder.DecodeInstruction();
+        
+        // Assert
+        Assert.NotNull(instruction);
+        Assert.Equal("scas", instruction.Mnemonic);
+        Assert.Equal("al, byte ptr [edi]", instruction.Operands);
+    }
 }