containsOnly results should render the expected value when a check fails

[scottford-io]

Describe the bug

The check above calls containsOnly with a specific string in an array. When the check fails the results show the check expected: == _ which is confusing since the check is clearly expecting ['S-1-5-32-544']

Expected behavior

[failed] [].containsOnly()
  expected: == ['S-1-5-32-544']
  actual:   [
    0: "S-1-5-32-550"
  ]