test-failing.js

var less = require('less');
 
less.render('@import "missingfile.less";\n.class { width: (1 + 1) }', function (err, output) {
    // err has error (missingfile.less does not exist)
    console.log("callback works but does not display any errors.");
    callUndefinedFunction();
    console.log("execution stopped, no errors in either stdout or stderr.");
});