Edit the data-es5.js, data-es6.js, data-es7.js, or data-non-standard.js files to adjust the tests and their recorded browser results. Run node build.js to build the HTML files from these JavaScript sources.
The tests themselves should be written in pure ES3, except for the sole ES6 feature being tested (as well as any ES5 features strictly required to use the ES6 feature). The test code is placed in multi-line comments (as in this hack), so that node can parse the data scripts without throwing syntax errors. The build.js script will wrap the code in an eval call inside a try, so the tests themselves do not need to catch errors that non-supporting platforms may throw.