QUnit Canvas assertion plugin

This plugin for QUnit adds pixelEqual and notPixelEqual (plus alias pixelNotEqual) assertion methods to test individual pixel values in a given canvas.

Usage

``js
assert.pixelEqual(canvas, x, y, r, g, b, a, message);
assert.notPixelEqual(canvas, x, y, r, g, b, a, message); // Alias: assert.pixelNotEqual
`

Where:
- canvas: Reference to a canvas element
- x, y: Coordinates of the pixel to test
- r, g, b: The color value (0-255) of the pixel that you expect
- a: The opacity value (0-255) of the pixel that you expect; may be omitted or passed undefined if you want to ignore it
- message: Optional message, same as for other assertions




Examples

`js
module('Example module', {
setup: function() {
var canvas, context,
fixtureEl = document.getElementById('qunit-fixture');
fixtureEl.innerHTML = '';

canvas = fixtureEl.firstChild;
try {
context = canvas.getContext('2d');
}
catch(e) {
// probably no canvas support, just exit
return;
}

this.canvas = canvas;
this.context = context;
}
});

test('Example unit test', function(assert) {
this.context.fillStyle = 'rgba(0, 0, 0, 0)';
this.context.fillRect(0, 0, 5, 5);

assert.pixelEqual(this.canvas, 0, 0, 0, 0, 0, 0);
assert.notPixelEqual(this.canvas, 0, 0, 1, 1, 1, 0);
});
``

For more examples, refer to the unit tests.

Contributing

In lieu of a formal styleguide, take care to maintain the existing coding style. Add unit tests for any new or changed functionality. Lint and test your code using grunt.