fix test

test/samples/export-not-at-top-level-fails/_config.js

@@ -1,8 +1,11 @@
+var path = require( 'path' );
 var assert = require( 'assert' );
 
 module.exports = {
 	description: 'disallows non-top-level exports',
 	error: function ( err ) {
-		assert.ok( false, 'TODO: pick an error message' );
+		assert.equal( err.file, path.resolve( __dirname, 'main.js' ) );
+		assert.deepEqual( err.loc, { line: 2, column: 2 });
+		assert.ok( /may only appear at the top level/.test( err.message ) );
 	}
 };