### Question:
Pair { @Override public String toString() { return "Pair [key=" + key + ", value=" + value + "]"; } Pair(final String key, final String value); String getKey(); String getValue(); @Override String toString();  }### Answer:
@Test public void testNullItems() { Pair nullPair = new Pair(null, null); assertEquals("Pair [key=null, value=null]", nullPair.toString()); }