ParkanPlayground/X86DisassemblerTests/AndInstructionTests.cs

namespace X86DisassemblerTests;

using System;
using Xunit;
using X86Disassembler.X86;

/// <summary>
/// Tests for AND instruction handlers
/// </summary>
public class AndInstructionTests
{
    /// <summary>
    /// Tests the AndImmWithRm32Handler for decoding AND r/m32, imm32 instruction
    /// </summary>
    [Fact]
    public void AndImmWithRm32Handler_DecodesAndRm32Imm32_Correctly()
    {
        // Arrange
        // AND EAX, 0x12345678 (81 E0 78 56 34 12) - ModR/M byte E0 = 11 100 000 (mod=3, reg=4, rm=0)
        // mod=3 means direct register addressing, reg=4 is the AND opcode extension, rm=0 is EAX
        byte[] codeBuffer = new byte[] { 0x81, 0xE0, 0x78, 0x56, 0x34, 0x12 };
        var decoder = new InstructionDecoder(codeBuffer, codeBuffer.Length);
        
        // Act
        var instruction = decoder.DecodeInstruction();
        
        // Assert
        Assert.NotNull(instruction);
        Assert.Equal("and", instruction.Mnemonic);
        Assert.Equal("eax, 0x12345678", instruction.Operands);
    }
    
    /// <summary>
    /// Tests the AndImmWithRm32SignExtendedHandler for decoding AND r/m32, imm8 instruction
    /// </summary>
    [Fact]
    public void AndImmWithRm32SignExtendedHandler_DecodesAndRm32Imm8_Correctly()
    {
        // Arrange
        // AND EAX, 0x42 (83 E0 42) - ModR/M byte E0 = 11 100 000 (mod=3, reg=4, rm=0)
        // mod=3 means direct register addressing, reg=4 is the AND opcode extension, rm=0 is EAX
        byte[] codeBuffer = new byte[] { 0x83, 0xE0, 0x42 };
        var decoder = new InstructionDecoder(codeBuffer, codeBuffer.Length);
        
        // Act
        var instruction = decoder.DecodeInstruction();
        
        // Assert
        Assert.NotNull(instruction);
        Assert.Equal("and", instruction.Mnemonic);
        Assert.Equal("eax, 0x00000042", instruction.Operands);
    }
    
    /// <summary>
    /// Tests the AND r32, r/m32 instruction
    /// </summary>
    [Fact]
    public void And_DecodesAndR32Rm32_Correctly()
    {
        // Arrange
        // AND EAX, ECX (23 C1) - ModR/M byte C1 = 11 000 001 (mod=3, reg=0, rm=1)
        // mod=3 means direct register addressing, reg=0 is EAX, rm=1 is ECX
        byte[] codeBuffer = new byte[] { 0x23, 0xC1 };
        var decoder = new InstructionDecoder(codeBuffer, codeBuffer.Length);
        
        // Act
        var instruction = decoder.DecodeInstruction();
        
        // Assert
        Assert.NotNull(instruction);
        Assert.Equal("and", instruction.Mnemonic);
        Assert.Equal("eax, ecx", instruction.Operands);
    }
    
    /// <summary>
    /// Tests the AND r/m32, r32 instruction
    /// </summary>
    [Fact]
    public void And_DecodesAndRm32R32_Correctly()
    {
        // Arrange
        // AND ECX, EAX (21 C1) - ModR/M byte C1 = 11 000 001 (mod=3, reg=0, rm=1)
        // mod=3 means direct register addressing, reg=0 is EAX, rm=1 is ECX
        byte[] codeBuffer = new byte[] { 0x21, 0xC1 };
        var decoder = new InstructionDecoder(codeBuffer, codeBuffer.Length);
        
        // Act
        var instruction = decoder.DecodeInstruction();
        
        // Assert
        Assert.NotNull(instruction);
        Assert.Equal("and", instruction.Mnemonic);
        Assert.Equal("ecx, eax", instruction.Operands);
    }
}