### Question:
DataDogIdentifier { @Override public boolean equals (Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; DataDogIdentifier that = (DataDogIdentifier) o; if (!key.equals(that.key)) return false; return value.equals(that.value); } private  DataDogIdentifier(); static DataDogIdentifier dataDogIdentifier(); @Override int hashCode(); @Override boolean equals(Object o); String getKey(); String getValue(); DataDogIdentifier withKey(String key); DataDogIdentifier withValue(String value); @Override String toString();  }### Answer:
@Test public void testEquals () { assertEquals(identifier, identifier); assertNotEquals(identifier, secondIdentifier); assertNotEquals(identifier, new Object()); }