### Question:
CRUDJsonNodeBuilder extends JsonNodeBuilder { public JsonNodeBuilder add(String key, QueryExpression value) { if (include(value)) { getRoot().put(key, value.toString().toLowerCase()); } return this; }  JsonNodeBuilder add(String key, QueryExpression value); JsonNodeBuilder add(String key, Projection value); JsonNodeBuilder add(String key, UpdateExpression value);  }### Answer:
@Test public void testAddQueryExpressionNull() { builder.add("query", (QueryExpression) null); assertNull(builder.build().get("query")); }