Mocha测试仅在通过调用时通过，但在与其他测试一起运行时会引发错误

Question

第二次运行它时，它运行良好。仅当我同时运行它们时，我收到一条错误消息：“无法读取null的属性'driving'。”

在第一个测试结束之前，DELETE测试似乎正在接触数据库。如何防止这种情况发生？

describe('Drivers controller', () => {    
  it('PUT to /api/drivers/:id edits an existing driver', done => {
    const driver = new Driver({ email: 't@t.com', driving: false });
    driver.save()
      .then(() => {
        chai.request(app)
          .put(`/api/drivers/${driver._id}`)
          .send({ driving: true})
          .end(() => {
            Driver.findOne({ email: 't@t.com' })
              .then(d => {
                assert(d.driving === true);
              });
          });
      })
      .then(() => done());
  });

  it('DELETE request to /api/drivers/:id removes an existing user', done => {
    const driver = new Driver({ email: 'test@test.com' });

    driver.save().then(() => {
      Driver.findOne({ email: 'test@test.com' })
        .then(driver => assert(driver !== null))
        .then(() => {
          chai.request(app)
            .delete(`/api/drivers/${driver._id}`)
            .end(() => {
              Driver.findOne({ email: 'test@test.com' }).then(driver => {
                assert(driver === null);
                done();
              });
            });
        });
    });
  });
});