"should mask first 4 characters/letters":
  input:
    - 'ab-cde-123'
    - '123.abc.420'
    - '3abc-0010.xy'
    - '1234567.a'
    - 'a-1234-bc'
    - 'a.b.c.d.e.f'
  expect:
    - 'xx-xxe-123'
    - 'xxx.xbc.420'
    - 'xxxx-0010.xy'
    - 'xxxx567.a'
    - 'x-xxx4-bc'
    - 'x.x.x.x.e.f'