lib/Assertion.php
function startWith(string $value): self {
    return $this->expect($this->target, stringStartsWith($value));
  }
function startWith(string $value): self {
    return $this->expect($this->target, stringStartsWith($value));
  }
Reports an error if the target does not start with the specified prefix.
@param string $value The prefix to check.
@return self This instance.