nes-emu/cpu/CPU.spec.js

A NES emulator

"use strict";

var _memory = require("../memory");
var _constants = require("./constants");
var _constants2 = _interopRequireDefault(require("../constants"));
var _createTestContext = _interopRequireDefault(require("../helpers/createTestContext"));
var _helpers = require("../helpers");
var _lodash = _interopRequireDefault(require("lodash"));
function _interopRequireDefault(e) { return e && e.__esModule ? e : { default: e }; }
const should = require("chai").Should();
const registersOf = cpu => _lodash.default.mapValues(cpu.registers, reg => reg.value);
describe("CPU", () => {
  let cpu, memory;
  beforeEach(() => {
    ({
      cpu,
      memory
    } = (0, _createTestContext.default)(context => {
      // mock the whole memory map
      const memory = new _memory.MemoryChunk(_constants2.default.CPU_ADDRESSED_MEMORY);
      _helpers.WithContext.apply(memory);
      context.cpu.memory = memory;

      // define sample program: NOP ; LDA #$05 ; STA $0201
      memory.write2BytesAt(_constants.interrupts.RESET.vector, 0x1234);
      [0xea, 0xa9, 0x05, 0x8d, 0x01, 0x02].forEach((byte, i) => memory.writeAt(0x1234 + i, byte));
    }));
  });
  it("initializes all variables", () => {
    cpu.pc.value.should.equal(0x1234);
    cpu.sp.value.should.equal(0xfd);
    cpu.flags.should.include({
      n: false,
      v: false,
      d: false,
      i: true,
      z: false,
      c: false
    });
    cpu.cycle.should.equal(7);
    registersOf(cpu).should.include({
      x: 0,
      y: 0,
      a: 0
    });
  });
  it("can run 3 simple operations", () => {
    let cycles;
    cycles = cpu.step();
    cycles.should.equal(2);
    cpu.pc.value.should.equal(0x1235);
    cpu.cycle.should.equal(9);
    cycles = cpu.step();
    cycles.should.equal(2);
    cpu.pc.value.should.equal(0x1237);
    cpu.cycle.should.equal(11);
    cpu.registers.a.value.should.equal(5);
    cycles = cpu.step();
    cycles.should.equal(4);
    cpu.pc.value.should.equal(0x123a);
    cpu.cycle.should.equal(15);
    memory.readAt(0x0201).should.equal(5);
  });
  _lodash.default.values(_constants.interrupts).forEach(interrupt => {
    it("can handle ".concat(interrupt.id, " interrupts"), () => {
      cpu.step();
      cpu.pc.value.should.equal(0x1235);
      cpu.flags.i = false;
      memory.write2BytesAt(interrupt.vector, 0x3125);
      cpu.interrupt(interrupt);
      cpu.stack.pop().should.equal(0b00100000);
      cpu.stack.pop2Bytes().should.equal(0x1235);
      cpu.cycle.should.equal(16);
      cpu.flags.i.should.equal(true);
      cpu.pc.value.should.equal(0x3125);
    });
  });
  it("ignores IRQ interrupts when the I flag is set", () => {
    cpu.step();
    cpu.pc.value.should.equal(0x1235);
    cpu.flags.i = true;
    memory.write2BytesAt(_constants.interrupts.IRQ.vector, 0x3125);
    cpu.interrupt(_constants.interrupts.IRQ);
    cpu.sp.value.should.equal(0xfd);
    cpu.cycle.should.equal(9);
    cpu.flags.i.should.equal(true);
    cpu.pc.value.should.equal(0x1235);
  });
});