qunit-assert-canvas

A QUnit plugin for asserting individual pixel values within a Canvas element.

npm install qunit-assert-canvas
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QUnit Canvas assertion plugin

This plugin for QUnit adds a pixelEqual assertion method to test individual pixel values in a given canvas.

Usage

assert.pixelEqual(canvas, x, y, r, g, b, a, message);

Where:

  • canvas: Reference to a canvas element
  • x, y: Coordinates of the pixel to test
  • r, g, b, a: The color and opacity value of the pixel that you except
  • message: Optional message, same as for other assertions

Example

module('Example module', {
  setup: function() {
    var canvas, context,
        fixtureEl = document.getElementById('qunit-fixture');
    fixtureEl.innerHTML = '<canvas width="5" height="5"></canvas>';

    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);
});

For more examples, refer to the unit tests.

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