diff --git a/index.html b/index.html
index 6eceef8f..bf00a0ab 100644
--- a/index.html
+++ b/index.html
@@ -1,7 +1,7 @@
 <!DOCTYPE html>
 <html lang="en">
 <head>
-<title>8bitworkshop ~ Atari 2600</title>
+<title>8bitworkshop</title>
 <style type="text/css" media="screen">
 body {
   overflow: hidden !important;
@@ -274,6 +274,10 @@ canvas {
 <script src="src/util.js"></script>
 <script src="src/disasm.js"></script>
 <script src="src/ui.js"></script>
+<script>
+  showWelcomeMessage();
+  startUI(true);
+</script>
 
 </body>
 <script>
diff --git a/package.json b/package.json
index 9d930331..820eee5e 100644
--- a/package.json
+++ b/package.json
@@ -14,7 +14,9 @@
     "test": "tests"
   },
   "scripts": {
-    "test": "mocha --recursive"
+    "test": "npm run test-node && npm run test-browser",
+    "test-node": "mocha --recursive test/cli",
+    "test-browser": "mocha-phantomjs ./testemu.html"
   },
   "repository": {
     "type": "git",
diff --git a/src/emu.js b/src/emu.js
index 0564c310..028de4b1 100644
--- a/src/emu.js
+++ b/src/emu.js
@@ -47,7 +47,7 @@ var RasterVideo = function(mainElement, width, height, options) {
     ctx = canvas.getContext('2d');
     imageData = ctx.createImageData(width, height);
     var buf = new ArrayBuffer(imageData.data.length);
-    buf8 = new Uint8ClampedArray(buf);
+    buf8 = new Uint8Array(buf); // TODO: Uint8ClampedArray
     datau32 = new Uint32Array(buf);
   }
 
@@ -235,8 +235,10 @@ var SampleAudio = function(clockfreq) {
   function createContext() {
     if ( typeof AudioContext !== 'undefined') {
       self.context = new AudioContext();
-    } else {
+    } else if (typeof webkitAudioContext !== 'undefined' ){
       self.context = new webkitAudioContext();
+    } else {
+      return;
     }
     self.sr=self.context.sampleRate;
     self.bufferlen=(self.sr > 44100) ? 4096 : 2048;
@@ -514,15 +516,14 @@ var BaseZ80Platform = function() {
     debugCondition = debugCond;
     this.resume();
   }
-  /*
   this.restartDebugState = function() {
     if (debugCondition && !debugBreakState) {
-      debugTargetClock -= cpu.getTstates();
-      cpu.setTstates(0);
       debugSavedState = this.saveState();
+      debugTargetClock -= debugSavedState.tstates;
+      debugSavedState.tstates = 0;
+      this.loadState(debugSavedState);
     }
   }
-  */
   this.getDebugCallback = function() {
     return debugCondition;
   }
diff --git a/src/platform/spaceinv.js b/src/platform/spaceinv.js
index 9529126f..69d458e5 100644
--- a/src/platform/spaceinv.js
+++ b/src/platform/spaceinv.js
@@ -15,7 +15,7 @@ var SpaceInvadersPlatform = function(mainElement) {
   this.__proto__ = new BaseZ80Platform();
 
   var cpu, ram, membus, iobus, rom;
-  var video, audio, timer, pixels;
+  var video, audio, timer, pixels, displayPCs;
   var inputs = [0xe,0x8,0x0];
   var bitshift_offset = 0;
   var bitshift_register = 0;
@@ -54,6 +54,7 @@ var SpaceInvadersPlatform = function(mainElement) {
 
   this.start = function() {
     ram = new RAM(0x2000);
+    displayPCs = new Uint16Array(new ArrayBuffer(0x2000*2));
     membus = {
       read: function(address) {
         if (address < 0x2000) {
@@ -74,6 +75,7 @@ var SpaceInvadersPlatform = function(mainElement) {
             var ofs = (address - 0x400)*8;
             for (var i=0; i<8; i++)
               pixels[ofs+i] = (value & (1<<i)) ? PIXEL_ON : PIXEL_OFF;
+            displayPCs[address] = cpu.getPC(); // save program counter
           }
         }
       },
@@ -137,15 +139,20 @@ var SpaceInvadersPlatform = function(mainElement) {
     timer = new AnimationTimer(60, function() {
 			if (!self.isRunning())
 				return;
-      cpu.setTstates(0);
       var debugCond = self.getDebugCallback();
+      var targetTstates = cpu.getTstates();
       for (var sl=0; sl<224; sl++) {
-        var targetTstates = cpu.getTstates() + cpuCyclesPerLine;
+        targetTstates += cpuCyclesPerLine;
         if (debugCond) {
           while (cpu.getTstates() < targetTstates) {
-            if (debugCond && debugCond()) { debugCond = null; }
+            if (debugCond && debugCond()) {
+              debugCond = null;
+              break;
+            }
             cpu.runFrame(cpu.getTstates() + 1);
           }
+          if (!debugCond)
+            break;
         } else {
           cpu.runFrame(targetTstates);
         }
@@ -159,7 +166,7 @@ var SpaceInvadersPlatform = function(mainElement) {
         console.log("WATCHDOG FIRED"); // TODO: alert on video
         self.reset();
       }
-      //self.restartDebugState();
+      self.restartDebugState();
     });
   }
 
diff --git a/src/ui.js b/src/ui.js
index fdd64993..d1f6c792 100644
--- a/src/ui.js
+++ b/src/ui.js
@@ -847,51 +847,60 @@ var qs = (function (a) {
     return b;
 })(window.location.search.substr(1).split('&'));
 
-// start
-showWelcomeMessage();
-// parse query string
-// is this a share URL?
-if (qs['sharekey']) {
-  var sharekey = qs['sharekey'];
-  console.log("Loading shared file ", sharekey);
-  $.getJSON( ".storage/" + sharekey, function( result ) {
-    console.log(result);
-    var newid = 'shared/' + result['filename'];
-    updatePreset(newid, result['text']);
-    qs['file'] = newid;
-    delete qs['sharekey'];
-    window.location = "?" + $.param(qs);
-  }, 'text');
-} else {
-  // reset file?
-  if (qs['file'] && qs['reset']) {
-    store.deleteFile(qs['file']);
-    qs['reset'] = '';
-    window.location = "?" + $.param(qs);
+function startPlatform() {
+  platform = new PLATFORMS[platform_id]($("#emulator")[0]);
+  store = new FileStore(localStorage, platform_id + '/');
+  PRESETS = platform.getPresets();
+  setupDebugControls();
+  platform.start();
+  if (qs['file']) {
+    // load file
+    loadPreset(qs['file']);
+    updateSelector();
   } else {
-    // add default platform?
-    platform_id = qs['platform'] || localStorage.getItem("__lastplatform");
-    if (!platform_id) {
-      platform_id = qs['platform'] = "vcs";
-    }
-    // load and start platform object
-    $.getScript('src/platform/' + platform_id + '.js', function() {
-      platform = new PLATFORMS[platform_id]($("#emulator")[0]);
-      console.log("loaded platform", platform_id);
-      store = new FileStore(localStorage, platform_id + '/');
-      PRESETS = platform.getPresets();
-      setupDebugControls();
-      platform.start();
-      if (qs['file']) {
-        // load file
-        loadPreset(qs['file']);
-        updateSelector();
-      } else {
-        // try to load last file
-        var lastid = localStorage.getItem("__lastid_"+platform_id) || localStorage.getItem("__lastid");
-        localStorage.removeItem("__lastid");
-        gotoPresetNamed(lastid || PRESETS[0].id);
-      }
-    });
+    // try to load last file
+    var lastid = localStorage.getItem("__lastid_"+platform_id) || localStorage.getItem("__lastid");
+    localStorage.removeItem("__lastid");
+    gotoPresetNamed(lastid || PRESETS[0].id);
+  }
+}
+
+// start
+function startUI(loadplatform) {
+  // parse query string
+  // is this a share URL?
+  if (qs['sharekey']) {
+    var sharekey = qs['sharekey'];
+    console.log("Loading shared file ", sharekey);
+    $.getJSON( ".storage/" + sharekey, function( result ) {
+      console.log(result);
+      var newid = 'shared/' + result['filename'];
+      updatePreset(newid, result['text']);
+      qs['file'] = newid;
+      delete qs['sharekey'];
+      window.location = "?" + $.param(qs);
+    }, 'text');
+  } else {
+    // reset file?
+    if (qs['file'] && qs['reset']) {
+      store.deleteFile(qs['file']);
+      qs['reset'] = '';
+      window.location = "?" + $.param(qs);
+    } else {
+      // add default platform?
+      platform_id = qs['platform'] || localStorage.getItem("__lastplatform");
+      if (!platform_id) {
+        platform_id = qs['platform'] = "vcs";
+      }
+      // load and start platform object
+      if (loadplatform) {
+        $.getScript('src/platform/' + platform_id + '.js', function() {
+          console.log("loaded platform", platform_id);
+          startPlatform();
+        });
+      } else {
+        startPlatform();
+      }
+    }
   }
 }
diff --git a/test/worker.js b/test/cli/worker.js
similarity index 100%
rename from test/worker.js
rename to test/cli/worker.js
diff --git a/test/z80/README b/test/cli/z80/README
similarity index 100%
rename from test/z80/README
rename to test/cli/z80/README
diff --git a/test/z80/test.html b/test/cli/z80/test.html
similarity index 99%
rename from test/z80/test.html
rename to test/cli/z80/test.html
index 1563daa3..3d0c31dd 100644
--- a/test/z80/test.html
+++ b/test/cli/z80/test.html
@@ -1,22 +1,22 @@
 <!DOCTYPE HTML>
 <!--
 	test.html: Test harness for the JSSpeccy Z80 core
-	
+
 	Copyright (C) 2009 Matthew Westcott
-	
+
 	This program is free software: you can redistribute it and/or modify
 	it under the terms of the GNU General Public License as published by
 	the Free Software Foundation, either version 3 of the License, or
 	(at your option) any later version.
-	
+
 	This program is distributed in the hope that it will be useful,
 	but WITHOUT ANY WARRANTY; without even the implied warranty of
 	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 	GNU General Public License for more details.
-	
+
 	You should have received a copy of the GNU General Public License
 	along with this program.  If not, see <http://www.gnu.org/licenses/>.
-	
+
 	Contact details: <matthew@west.co.tt>
 	Matthew Westcott, 14 Daisy Hill Drive, Adlington, Chorley, Lancs PR6 9NE UNITED KINGDOM
 -->
@@ -24,7 +24,7 @@
 	<head>
 		<title>jsspeccy test</title>
 		<script>var global = {}</script>
-		<script src="../../src/cpu/z80.js"></script>
+		<script src="../../../src/cpu/z80.js"></script>
 		<script type="text/javascript">/* <![CDATA[ */
 			var testInputLines;
 			var currentLine;
diff --git a/test/z80/tests.expected b/test/cli/z80/tests.expected
similarity index 100%
rename from test/z80/tests.expected
rename to test/cli/z80/tests.expected
diff --git a/test/z80/tests.in b/test/cli/z80/tests.in
similarity index 100%
rename from test/z80/tests.in
rename to test/cli/z80/tests.in
diff --git a/test/z80/z80test.js b/test/cli/z80/z80test.js
similarity index 96%
rename from test/z80/z80test.js
rename to test/cli/z80/z80test.js
index 591d8243..1975968b 100644
--- a/test/z80/z80test.js
+++ b/test/cli/z80/z80test.js
@@ -1,6 +1,6 @@
 "use strict";
 
-require('../../src/cpu/z80.js');
+require('../../../src/cpu/z80.js');
 
 var _global = window;
 
@@ -196,8 +196,8 @@ function hexWord(num) {
 
 var fs = require('fs');
 var assert = require('assert');
-var testsIn = fs.readFileSync('test/z80/tests.in', {encoding:'utf8'}).split('\n\n');
-var testsExpected = fs.readFileSync('test/z80/tests.expected', {encoding:'utf8'}).split('\n\n');
+var testsIn = fs.readFileSync('test/cli/z80/tests.in', {encoding:'utf8'}).split('\n\n');
+var testsExpected = fs.readFileSync('test/cli/z80/tests.expected', {encoding:'utf8'}).split('\n\n');
 assert(testsIn.length == testsExpected.length);
 
 describe('Z80 CPU', function() {
diff --git a/test/ui/testemus.js b/test/ui/testemus.js
new file mode 100644
index 00000000..9d1584ad
--- /dev/null
+++ b/test/ui/testemus.js
@@ -0,0 +1,26 @@
+
+function assert(b, msg) {
+  if (!b) { throw new Error(msg); }
+}
+
+describe('Test VCS emulator', function() {
+  var platform = new VCSPlatform();
+  it('Should start', function(done) {
+    platform.start();
+    assert(!platform.isRunning());
+    // TODO: more testing
+    done();
+  });
+});
+
+describe('Test Space Invaders emulator', function() {
+  var platform = new SpaceInvadersPlatform($('#emulator')[0]);
+  it('Should start', function(done) {
+    platform.start();
+    assert(!platform.isRunning());
+    platform.resume();
+    assert(platform.isRunning());
+    // TODO: more testing
+    done();
+  });
+});
diff --git a/testemu.html b/testemu.html
new file mode 100644
index 00000000..4b57769e
--- /dev/null
+++ b/testemu.html
@@ -0,0 +1,46 @@
+
+<html>
+  <head>
+    <meta charset="utf-8">
+    <!-- encoding must be set for mocha's special characters to render properly -->
+    <link rel="stylesheet" href="node_modules/mocha/mocha.css" />
+  </head>
+  <body>
+    <div id="mocha"></div>
+    <div id="notebook">
+      <div id="editor_window">
+        <div id="disassembly" class="editor">
+        </div>
+        <div id="editor" class="editor">
+        </div>
+      </div>
+      <div class="emulator" id="emulator">
+        <div id="javatari-screen" style="margin: 0 auto; box-shadow: 2px 2px 10px rgb(60, 60, 60);"></div>
+        <div id="javatari-console-panel" style="margin: 0 auto; box-shadow: 2px 2px 10px rgb(60, 60, 60);"></div>
+        <div id="mem_info" class="mem_info" style="display:none">
+        </div>
+      </div>
+    </div>
+    <script src="node_modules/mocha/mocha.js"></script>
+
+    <script>
+      mocha.ui('bdd')
+    </script>
+
+    <script src="jquery/jquery-2.2.3.min.js"></script>
+
+    <script src="javatari.js/release/javatari/javatari.js"></script>
+    <script src="src/cpu/z80.js"></script>
+    <script src="src/emu.js"></script>
+    <script src="src/util.js"></script>
+    <script src="src/disasm.js"></script>
+    <script src="src/platform/vcs.js"></script>
+    <script src="src/platform/spaceinv.js"></script>
+
+    <script src="test/ui/testemus.js"></script>
+
+    <script>
+      mocha.run()
+    </script>
+  </body>
+</html>
