test case for execify/1

gulpfile.js

var gulp = require('gulp');
var es = require('event-stream');
var path = require('path');

var filePath = path.join(__dirname, 'gulpfile.js');
var expectedFile;

function plugalug() {
  return es.map(function(file, cb) {
    if (typeof file === 'undefined') {
      throw new Error('File was undefined!');
    }
    else {
      expectedFile = file;
    }
    cb(null, file);
  });
}

gulp.task('test', function() {
  var stream = gulp.src(filePath)
    .pipe(plugalug());
  stream.once('end', function() {
    console.assert(expectedFile, 'File should be defined');
    console.assert(expectedFile.path === filePath, 'Path should be correct');
    console.log('Stream ended and all is well!');
  });
  return stream;
})

gulp.task('default', function() {
  gulp.run('test')
});