Added a small utility for bit manipulation. Tests included.

package.json

   "description": "Fantasy 8Bit (F8) chip emulator",
   "main": "f8.js",
   "scripts": {
-    "test": "mocha"
+    "test": "mocha -R spec --recursive"
   },
   "keywords": [
     "fantasy",

src/utils/bitman.js

+
+var bitman = {};
+
+bitman.isOn = function(num, bit){
+  return ((num>>bit) % 2) !== 0;
+}
+
+bitman.set = function(num, bit){
+  return num | (1<<bit);
+}
+
+bitman.clear = function(num, bit){
+  return num & ~(1<<bit);
+}
+
+bitman.toggle = function(num, bit){
+  return (bitman.isOn(num, bit)) ? 
+    bitman.clear(num, bit) : 
+    bitman.set(num, bit);
+}
+
+
+module.exports = bitman;

test/utils/bitman.spec.js

+const BIT = require('../../src/utils/bitman.js');
+const expect = require('chai').expect;
+
+describe("Testing utils/bitman ...", function(){
+  it(".isOn() 'true' test", function(){
+    expect(BIT.isOn(parseInt("0010", 2), 1)).be.true;
+  });
+
+  it(".isOn() 'false' test", function(){
+    expect(BIT.isOn(parseInt('0111', 2), 3)).be.false;
+  });
+
+  it(".set()", function(){
+    let num = 1;
+    num = BIT.set(num, 1);
+    expect(num).to.equal(3);
+  });
+
+  it(".clear()", function(){
+    let num = 15;
+    num = BIT.clear(num, 2);
+    expect(num).to.equal(11);
+  });
+
+  it(".toggle()", function(){
+    let num = 9;
+    num = BIT.toggle(num, 3);
+    num = BIT.toggle(num, 2);
+    expect(num).to.equal(5);
+  });
+});