molecule test: default embedded docker driver would not be invoked to start docker container

[shanxijie]

For whatever reason, the default embedded docker driver would not be invoked to start docker container when I run "molecule test". I kept to get the message for asking me to provide playbook to step create:
...
--> Action: 'create'
Skipping, create action has no playbook.
...

Here is my molecule.yml:

---

dependency:
name: galaxy
driver:
name: docker
platforms:

• name: instance
  image: docker.io/pycontribs/centos:8
  pre_build_image: true
  provisioner:
  name: ansible
  verifier:
  name: ansible

It supposes to use default docker driver to start centos8 container, but it did not.