private static IntPredicate isReservedChar(){
    return RESERVED_CHARACTERS.codePoints()
      .mapToObj(codePoint -> (IntPredicate) other -> codePoint == other)
      .reduce(IntPredicate::or)
      .orElseThrow(() -> new IllegalStateException("This should never happen (tm)"));
  }
Creates a new {@link TestTag} with the given value.

Must not contain any of the following characters:
<ul>
  <li>White Space</li>
  <li>ISO Control Characters</li>
  <li>{@code !}</li>
  <li>{@code &}</li>
  <li>{@code (}</li>
  <li>{@code )}</li>
  <li>{@code ,}</li>
  <li>{@code |}</li>
</ul>

@param tag the value of the tag
@return a new {@link TestTag}
spock-core/src/main/java/org/spockframework/runtime/model/TestTag.java