Support RE Matching

I implemented locally this one. This may help other people doing RE matching tests

```
assert_matches() {
  local expected=$1
  local actual=$2
  local message=${3:-}
  [[ -z $message ]] || message="$message\n"

  if [[ ! "${actual}" =~ ${expected} ]]; then
    fail "$message expected regex [$expected] to match [$actual]"
  fi
}
```