public void Test_PREFIX() { var expectedState = new CpuState(); expectedState.InstructionPrefix = true; var actualState = new CpuState(); var memoryMock = new Mock <IRandomAccessMemory>(); var instruction = new PREFIX(); instruction.Initialize(); //act while (!instruction.IsFetchNecessary()) { instruction.ExecuteCycle(actualState, memoryMock.Object); } TestHelper.AssertCpuState(expectedState, actualState); memoryMock.Verify(m => m.WriteByte(It.IsAny <ushort>(), It.IsAny <byte>()), Times.Never); }