Uncaught ReferenceError: describe is not defined using ndb

im trying to use ndb to debug my node js test . but i get an error:

Uncaught ReferenceError: describe is not defined

the test i try to debug is just a simple test code:

describe('one', () => {
    it('this test always passing', () => {
        expect(true).toBeTruthy();
    });
});

anyone knows what is the cuase for that?