public void ExecutingInstruction_WhichDoesNotModifyPc_IncreasesPcBy2()
{
var cpu = new Cpu();
cpu.Memory[Cpu.MemoryAddressOfFirstInstruction + 1] = 0xE0; // CLS instruction
Assert.That(cpu.PC, Is.EqualTo(Cpu.MemoryAddressOfFirstInstruction));
var instructionExecutor = new InstructionExecutor(cpu, _display, _keyboard, _instructionDecoder);
var instruction = instructionExecutor.ExecuteSingleInstruction();
Assert.That(instruction, Is.InstanceOf <Instruction_00E0>());
Assert.That(cpu.PC, Is.EqualTo(Cpu.MemoryAddressOfFirstInstruction + 2));
}
public void ExecutingInstruction_WhichModifiesPc_DoesNotAdditionallyIncreasePcBy2()
{
var cpu = new Cpu();
cpu.Stack.Push(Cpu.MemoryAddressOfFirstInstruction);
cpu.Memory[Cpu.MemoryAddressOfFirstInstruction + 1] = 0xEE; // RET instruction
Assert.That(cpu.PC, Is.EqualTo(Cpu.MemoryAddressOfFirstInstruction));
var instructionExecutor = new InstructionExecutor(cpu, _display, _keyboard, _instructionDecoder);
var instruction = instructionExecutor.ExecuteSingleInstruction();
Assert.That(instruction, Is.InstanceOf <Instruction_00EE>());
Assert.That(cpu.PC, Is.EqualTo(Cpu.MemoryAddressOfFirstInstruction));
}
public void ExecutingInstruction_WithEmptyMemory_ThrowsException()
{
var instructionExecutor = new InstructionExecutor(_cpu, _display, _keyboard, _instructionDecoder);
Assert.Throws <InvalidOperationException>(() => instructionExecutor.ExecuteSingleInstruction());
}