syntax error, unexpected tLABEL in Chef Test Kitchen

During the test of a Chef recipe that contains a template we may encounter the error message

syntax error, unexpected tLABEL
MY_KEY: MY_VALUE

Make sure there is no white space between the keyword variables and the opening parenthesis in the template definition:

template "MY_FILE" do
  source 'MY_SOURCE'
  variables(
    MY_KEY: MY_VALUE
  )
end