### Question:
TagExtractor { public void add(String line) { if (tag_ == target_ && line != null) { buf_.append(line); } } TagExtractor(String tag, int threshold); int count(); void clear(); void setTag(String tag); void add(String line); String closeTag();  }### Answer:
@Test public final void testAdd() { TagExtractor extractor = new TagExtractor(null, 0); extractor.add(""); extractor.add(null); }