Custom plugin not being detected

[emmaLP]

I'm new to molecule so learning as I go along.

I've got an existing ansible role that relies on a custom plugin gce_facts, I have created a a version of this to return dummy data for testing within docker. I've mounted mount the plugin into /usr/share/ansible/plugins/modules/dummy-gce-facts.

But when running molecule converge -- --extra-vars "cloud_provider=Google" I get the following error:

ERROR! couldn't resolve module/action 'gce_facts'. This often indicates a misspelling, missing collection, or incorrect module path.

The error appears to be in '/app/roles/master/tasks/main.yml': line 1, column 3, but may
be elsewhere in the file depending on the exact syntax problem.

The offending line appears to be:


- name: Gather instance facts | Google Cloud Platform
  ^ here

My molecule file looks like this:

--- 
dependency: 
  name: galaxy 
driver: 
  name: docker 
platforms: 
  - name: instance 
    #    image: docker.io/pycontribs/debian:latest 
    image: test-docker 
    pre_build_image: true 
    volumes: 
      - "/local-dev/dummy-gce-facts/:/usr/share/ansible/plugins/modules/dummy-gce-facts" 
    env: 
      ANSIBLE_LIBRARY: "/usr/share/ansible/plugins/modules/dummy-gce-facts:/usr/share/ansible/plugins/modules/:$ephemeral_directory/modules/:$project_directory/library/:~/.ansible/plugins/modules" 
lint: yamllint 
provisioner: 
  name: ansible 
verifier: 
  name: ansible

I'm using a custom docker image, generate with the following Dockerfile:

FROM debian:buster

RUN DEBIAN_FRONTEND=noninteractive \
    apt-get update -y && \
    apt-get install -y --no-install-recommends apt-utils gcc git python3 python3-dev python3-pip libssl-dev sudo && \
    rm -rf /var/lib/apt/lists/* && \
    mkdir -p /usr/share/ansible/plugins/modules

ENV SHELL /bin/bash

Ansible & Molecule Version:

ansible 2.9.12
  config file = None
  configured module search path = ['/root/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/local/lib/python3.7/dist-packages/ansible
  executable location = /usr/local/bin/ansible
  python version = 3.7.3 (default, Jul 25 2020, 13:03:44) [GCC 8.3.0]

molecule 3.0.8

Please could someone advise me on why molecule is not detecting the custom plugin even when set in a default ansible plugins location?
Really struggling to figure this out.