in junit-platform-engine/src/main/java/org/junit/platform/engine/TestTag.java [85:95]
public static boolean isValid(String name) {
if (name == null) {
return false;
}
name = name.trim();
return !name.isEmpty() && //
StringUtils.doesNotContainWhitespace(name) && //
StringUtils.doesNotContainIsoControlCharacter(name) && //
doesNotContainReservedCharacter(name);
}