@Test void testNoItems() { assertNull(underTest.build()); }
public String build() { if (items.isEmpty()) { return null; } else { return StringUtils.join(items, " "); } }
CssBuilder { public String build() { if (items.isEmpty()) { return null; } else { return StringUtils.join(items, " "); } } }
CssBuilder { public String build() { if (items.isEmpty()) { return null; } else { return StringUtils.join(items, " "); } }  }
CssBuilder { public String build() { if (items.isEmpty()) { return null; } else { return StringUtils.join(items, " "); } }  void add(String cssClass); String build(); @Override String toString(); }
CssBuilder { public String build() { if (items.isEmpty()) { return null; } else { return StringUtils.join(items, " "); } }  void add(String cssClass); String build(); @Override String toString();  }