text: import os.path as op
  
  from datalad.api import Dataset
  from datalad.api import create
  from datalad.api import containers_add
  from datalad.api import containers_list
  from datalad.api import containers_run
  from datalad.cmd import (
      StdOutCapture,
      WitlessRunner,
  )
  from datalad.tests.utils import ok_clean_git
  from datalad.tests.utils import ok_file_has_content
  from datalad.tests.utils import assert_result_count
  from datalad.tests.utils import with_tempfile
  from datalad.tests.utils import skip_if_no_network
  
  
  @skip_if_no_network
  @with_tempfile
  def test_docker(path):  # Singularity's "docker://" scheme.
      ds = Dataset(path).create()
      ds.containers_add(
          "bb",
          url=("docker://busybox@sha256:"
               "7964ad52e396a6e045c39b5a44438424ac52e12e4d5a25d94895f2058cb863a0"))
  
      img = op.join(ds.path, ".datalad", "environments", "bb", "image")
      assert_result_count(ds.containers_list(), 1, path=img, name="bb")
      ok_clean_git(path)
  
      WitlessRunner(cwd=ds.path).run(
          ["datalad", "containers-run", "ls", "/singularity"],
          protocol=StdOutCapture)
  