text: var acorn = require( 'acorn' );
  
  var modules = {
  	'main': 'import foo from \'foo\';\nfoo();',
  
  	// the code points to './bar' but the AST points to './baz', so we
  	// can check the AST is being used
  	'foo': {
  		code: 'import bar from \'bar\';\nexport default function foo () {\n\tconsole.log( bar );\n}',
  		ast: acorn.parse( 'import bar from \'baz\';\nexport default function foo () {\n\tconsole.log( bar );\n}', {
  			ecmaVersion: 6,
  			sourceType: 'module'
  		})
  	},
  
  	'baz': 'export default 42;'
  };
  
  module.exports = {
  	description: 'uses supplied AST',
  	options: {
  		plugins: [{
  			resolveId: function ( importee, importer ) {
  				if ( !importer ) return 'main';
  				return importee;
  			},
  			load: function ( id ) {
  				if ( id === 'bar' ) {
  					throw new Error( 'loaded incorrect module' );
  				}
  
  				return modules[ id ];
  			}
  		}]
  	}
  };
  