### Question:
EntityTagHeaderProvider implements HeaderDelegate<EntityTag> { public String toString(EntityTag tag) { StringBuilder sb = new StringBuilder(); if (tag.isWeak()) { sb.append(WEAK_PREFIX); } String tagValue = tag.getValue(); if (!tagValue.startsWith("\"")) { sb.append('"').append(tagValue).append('"'); } else { sb.append(tagValue); } return sb.toString(); }  EntityTag fromString(String header); String toString(EntityTag tag);  }### Answer:
@Test public void testToString() { EntityTag tag = new EntityTag(""); assertEquals("\"\"", tag.toString()); tag = new EntityTag("", true); assertEquals("W/\"\"", tag.toString()); tag = new EntityTag("bar"); assertEquals("\"bar\"", tag.toString()); }