[TEST][Proposal] Let test cases use same OS image configured in config.yml, thus easy to test OS support matrix.

[albinsun]

What's the test to develop? Please describe

Currently different test suite may have their own image setting, for example

• test_hosts.py uses ubuntu-20.04

  ...
  @pytest.fixture(scope="session")
  def focal_image_url(request):
    base_url = request.config.getoption("--image-cache-url").strip()
    base_url = base_url or "http://cloud-images.ubuntu.com/releases/focal/release"
    return urljoin(f"{base_url}/", "ubuntu-20.04-server-cloudimg-amd64-disk-kvm.img")
  ...

• test_rancher_integration.py uses focal-server-cloudimg

  ...
  @pytest.fixture(scope="module")
  def focal_image_url(request):
    external = 'https://cloud-images.ubuntu.com/focal/current/'
    base_url = request.config.getoption('--image-cache-url') or external
    return os.path.join(base_url, "focal-server-cloudimg-amd64.img")

• test_backup_restore.py uses opensuse leap

  ...
  @pytest.fixture(scope="module")
  def image(api_client, unique_name, wait_timeout, image_opensuse):
    unique_image_id = f'image-{unique_name}'
    code, data = api_client.images.create_by_url(
        unique_image_id, image_opensuse.url, display_name=f"{unique_name}-{image_opensuse.name}"
    )
  ...

• ...

We may change to image section in config.yml to something like

# URL to download the Windows image
win-image-url: ''
linux-image-url: http://192.168.123.1:8080/openSUSE-Leap-15.5.x86_64-NoCloud.qcow2
...

and refactor all test cases to use it, thus

1. We can have a concrete test result for specific OS version
2. To test different OS for support matrix, just change linux-image-url and run a complete test.

[albinsun]

cc. @khushboo-rancher, @bk201 and @lanfon72

[bk201]

+1 to this

[lanfon72]

let's put this into schedule. It would affect to fixtures and config options, and to be aware that if we are going to generalize the image, sshuser would need to be consider in the config option.