Pragmatic Unit Testing in Java with JUnit, 3rd Edition

Command-Query Separation

The only remaining oddity in Profile is how it handles scoring logic. Examine its matches method:

utj3-refactor/21/src/main/java/iloveyouboss/Profile.java

public boolean matches(Criteria criteria) {
    var matcher = new Matcher(criteria, answers);
    score = matcher.score();
    return matcher.matches();
}

As a side effect, Profile stores a score. But a profile doesn’t have a single fixed score. It only references a calculated score that’s associated with an attempt to match on criteria.

The score side effect causes another problem, which is that a client can’t separate one interest from the other. If a client wants (only) the score for a set of criteria, it must first call the matches() method. This sort ...