gm - alpha.js test file

var assert = require('assert')

module.exports = function (_, dir, next, gm) {

  if (!gm.integration) return next();

  var alphaTypes = [
    "Activate",
    "On",
    "Associate",
    "Deactivate",
    "Off",
    "Disassociate",
    "Set",
    "Opaque",
    "Transparent",
    "Extract",
    "Copy",
    "Shape",
    "Remove",
    "Background"
  ];

  assert.throws(function() {

    gm(dir + '/alpha.png')
      .alpha( alphaTypes.pop() )
      .write(dir + '/alpha_fail.png', function(err) {
        if (!err) next( new Error('Method -alpha is supposed to fail without ImageMagick option enabled.') );
		else {
			nextAlpha();
		}
      });

  }, Error);

  function nextAlpha() {
    test(alphaTypes.pop());
  }

  function test(alphaType) {

    var m = gm(dir + '/alpha.png')
        .options({ imageMagick: true })
        .alpha( alphaType );

    var args = m.args();
    assert.equal('convert', args[0]);
    assert.equal('-alpha', args[2]);
    assert.equal(alphaType, args[3]);

    m.write( dir + '/alpha_' + alphaType + '.png', function(err) {
      if (!err) next(err);
      else {
        if (alphaTypes.length) {
          nextAlpha();
        } else {
          next();
        }
      }
    });
  };
}