function _valToString(val)
{
	if (val === undefined || val === null)
		return '[' + typeof(val) + ']';
	return val.toString() + '[' + typeof(val) + ']';
}

var _failed = false;
var _asserted = false;
function _warn(text)
{
	document.getElementById('d').appendChild(document.createElement('li')).appendChild(document.createTextNode(text));
}
function _fail(text)
{
	_warn(text);
	_failed = true;
}

function _assert(cond, text)
{
	_asserted = true;
	if (! cond)
		_fail('Failed assertion: ' + text);
}

function _assertSame(a, b, text_a, text_b)
{
	_asserted = true;
	if (a !== b)
		_fail('Failed assertion ' + text_a + ' === ' + text_b +
				' (got ' + _valToString(a) + ', expected ' + _valToString(b) + ')');
}

function _assertDifferent(a, b, text_a, text_b)
{
	_asserted = true;
	if (a === b)
		_fail('Failed assertion ' + text_a + ' !== ' + text_b +
				' (got ' + _valToString(a) + ', expected not ' + _valToString(b) + ')');
}

function _assertEqual(a, b, text_a, text_b)
{
	_asserted = true;
	if (a != b)
		_fail('Failed assertion ' + text_a + ' == ' + text_b +
				' (got ' + _valToString(a) + ', expected ' + _valToString(b) + ')');
}

function _assertMatch(a, b, text_a, text_b)
{
	_asserted = true;
	if (! a.match(b))
		_fail('Failed assertion ' + text_a + ' matches ' + text_b +
				' (got ' + _valToString(a) + ')');
}


var _manual_check = false;

function _requireManualCheck()
{
	_manual_check = true;
}

function _crash()
{
	_fail('Aborted due to predicted crash');
}

function _getPixel(canvas, x,y)
{
	try {
		var ctx = canvas.getContext('2d');
		var imgdata = ctx.getImageData(x, y, 1, 1);
		return [ imgdata.data[0], imgdata.data[1], imgdata.data[2], imgdata.data[3] ];
	} catch (e) {
		// probably a security exception caused by having drawn
		// data: URLs onto the canvas
		_manual_check = true;
		return undefined;
	}
}

function _assertPixel(canvas, x,y, r,g,b,a, pos, colour)
{
	_asserted = true;
	var c = _getPixel(canvas, x,y);
	if (c && ! (c[0] == r && c[1] == g && c[2] == b && c[3] == a))
		_fail('Failed assertion: got pixel [' + c + '] at ('+x+','+y+'), expected ['+r+','+g+','+b+','+a+']');
}

function _assertPixelApprox(canvas, x,y, r,g,b,a, pos, colour, tolerance)
{
	_asserted = true;
	var c = _getPixel(canvas, x,y);
	if (c)
	{
		var diff = Math.max(Math.abs(c[0]-r), Math.abs(c[1]-g), Math.abs(c[2]-b), Math.abs(c[3]-a));
		if (diff > tolerance)
			_fail('Failed assertion: got pixel [' + c + '] at ('+x+','+y+'), expected ['+r+','+g+','+b+','+a+'] +/- '+tolerance);
	}
}

function _addTest(test)
{
	var deferred = false;
	window.deferTest = function () { deferred = true; };
	function endTest()
	{
		if (_failed) // test failed
		{
			document.documentElement.className += ' fail';
			window._testStatus = ['fail', document.getElementById('d').innerHTML];
		}
		else if (_manual_check || !_asserted)
		{ // test case explicitly asked for a manual check, or no automatic assertions were performed
			document.getElementById('d').innerHTML += '<li>Cannot automatically verify result';
			document.documentElement.className += ' needs_check';
			window._testStatus = ['check', document.getElementById('d').innerHTML];
		}
		else // test succeeded
		{
			document.getElementById('d').innerHTML += '<li>Passed';
			document.documentElement.className += ' pass';
			window._testStatus = ['pass', document.getElementById('d').innerHTML];
		}
	}
	window.endTest = endTest;
	window.wrapFunction = function (f)
	{
		return function()
		{
			try
			{
				f.apply(null, arguments);
			}
			catch (e)
			{
				_fail('Aborted with exception: ' + e.message);
			}
			endTest();
		}
	}

	window.onload = function ()
	{
		try
		{
			var canvas = document.getElementById('c');
			var ctx = canvas.getContext('2d');
			test(canvas, ctx);
		}
		catch (e)
		{
			_fail('Aborted with exception: ' + e.message);
			deferred = false; // cancel any deference
		}

		if (! deferred)
			endTest();
	};
}