public void Executing_Instruction_Dxyn_WorksAsExpected()
{
const byte xCoordinate = 0x5, yCoordinate = 0x6;
var cpu = new Cpu();
cpu.V[2] = xCoordinate;
cpu.V[3] = yCoordinate;
cpu.I = 0x300;
cpu.Memory[cpu.I] = 0x1;
var decodedInstruction = new DecodedInstruction(0xD231);
// Expected execution result:
// - decodedInstruction.n bytes (1) are read from memory, starting at location I (0x300)
// - those bytes are written to screen, starting at location (V2, V3) = 5,6
// - since value at 0x300 is 0x1, and 1 is the least significant bit of that byte, then location where
// pixel will be set is: xCoordinate + 7 (e.g. for value of 2, it would be xCoordinate + 6)
// - re-executing the same command will reset the pixel and set VF register to 1
var mockSequence = new MockSequence();
var displayMock = new Mock<IDisplay>(MockBehavior.Strict);
// First execution
for(byte i = 0; i < 8; i++)
{
displayMock.InSequence(mockSequence).Setup(x => x.GetPixel(
(byte)(xCoordinate + i), yCoordinate)).Returns(false);
}
displayMock.InSequence(mockSequence).Setup(x => x.SetPixel(xCoordinate + 7, yCoordinate));
// Second execution
for (byte i = 0; i < 8; i++)
{
displayMock.InSequence(mockSequence).Setup(x => x.GetPixel(
(byte)(xCoordinate + i), yCoordinate)).Returns(i == 7);
}
displayMock.InSequence(mockSequence).Setup(x => x.ClearPixel(xCoordinate + 7, yCoordinate));
var display = displayMock.Object;
var instruction = new Instruction_Dxyn(decodedInstruction);
instruction.Execute(cpu, display, MockedKeyboard);
Assert.That(cpu.V[0xF], Is.EqualTo(0));
instruction.Execute(cpu, display, MockedKeyboard);
Assert.That(cpu.V[0xF], Is.EqualTo(1));
displayMock.VerifyAll();
Assert.That(instruction.Mnemonic, Is.EqualTo($"DRW V{decodedInstruction.x:X}, V{decodedInstruction.y:X}, {decodedInstruction.n:X}"));
}
public void Executing_Instruction_Dxy0_DoesNotUseDisplay()
{
var cpu = new Cpu();
var decodedInstruction = new DecodedInstruction(0xD230);
var instruction = new Instruction_Dxyn(decodedInstruction);
instruction.Execute(cpu, MockedDisplay, MockedKeyboard);
}
