ferris-boi/tests/cpu/misc.rs

use ferris_boi::{
    cpu::{instructions::RunnableInstruction, Processor},
    register,
};
use test_case::test_case;
use crate::testutil;

#[test_case(1)]
#[test_case(0)]
fn test_set_carry_flag_always_sets_to_1(starting_value: u8) {
    let mut processor = Processor::default();
    processor
        .registers
        .set_flag_bit(register::Flag::Carry, starting_value);

    let data = [0x37, 0x03];
    let (ins, extra_data) =
        RunnableInstruction::from_data(&data).expect("could not parse instruction");

    assert_eq!(extra_data, &[0x03]);
    processor.run_instruction(&ins);

    let new_carry_bit = processor.registers.get_flag_bit(register::Flag::Carry);
    assert_eq!(1, new_carry_bit);
}

#[test_case(1, 0)]
#[test_case(0, 1)]
fn test_complement_carry_bit(starting_value: u8, expected_value: u8) {
    let mut processor = Processor::default();
    processor
        .registers
        .set_flag_bit(register::Flag::Carry, starting_value);

    let data = [0x3F, 0x03];
    let (ins, extra_data) =
        RunnableInstruction::from_data(&data).expect("could not parse instruction");

    assert_eq!(extra_data, &[0x03]);
    processor.run_instruction(&ins);

    let new_carry_bit = processor.registers.get_flag_bit(register::Flag::Carry);
    assert_eq!(expected_value, new_carry_bit);
}

#[test_case(0x37)]
#[test_case(0x3F)]
fn test_all_carry_bit_instructions_adjust_flags(opcode: u8) {
    let mut processor = Processor::default();
    testutil::set_opposite_of_expected_flags(&mut processor, (0, 0, 0, 1));

    let data = [opcode, 0x03];
    let (ins, extra_data) =
        RunnableInstruction::from_data(&data).expect("could not parse instruction");

    assert_eq!(extra_data, &[0x03]);
    processor.run_instruction(&ins);

    testutil::assert_flags_eq!(
        processor,
        // Always zero
        (register::Flag::HalfCarry, 0),
        (register::Flag::Carry, 1),
        (register::Flag::Subtract, 0),
        // Value is preserved
        (register::Flag::Zero, 1),
    );
}