javascript - Mocha test factorization and backtrace -

i run many mocha tests :

it('should fail blabla', function () {     return <functionthatreturnsapromise>()         .then(function () {             assert(false);         }, function (err) {             assert.strictequal(err.message, 'foobar undefined');             assert.strictequal(err.code, 'eundefinedfoobar');         }); }); 

the things vary among tests function, code , message.

i wanted factorize code this:

function shouldberejected(promise, code, message) {     return promise         .then(function () {             assert(false);         }, function (err) {             assert.strictequal(err.code, code);             assert.strictequal(err.message, message);         }); } (...) it('should fail blabla', function () {     return shouldberejected(<functionthatreturnsapromise>(),                             'eundefinedfoobar', 'foobar undefined'); }); 

it works when tests failed, backtraces reference shouldberejected function , so, i'm losing information real test failed.
there way more "intelligent" backtrace pointing shouldberejected calls indirectly raise error? maybe capturestacktrace somewhere?