lib/Assertion.php
function satisfy(callable $predicate): self {
    return $this->expect(call_user_func($predicate, $this->target), isTrue());
  }
function satisfy(callable $predicate): self {
    return $this->expect(call_user_func($predicate, $this->target), isTrue());
  }
Reports an error if the target does not pass a given truth test.
@param callable $predicate The predicate to invoke.
@return self This instance.