### Question:
DocumentConverter extends AbstractConverter<Document> { @Override protected String convertToString(Document value) { return this.serializer.serialize(value.getDocumentReference()); }  @Override G convert(Type targetType, Object sourceValue); @Override Document convertToType(Type targetType, Object sourceValue);  }### Answer:
@Test void convertToString() { when(serializer.serialize(document.getDocumentReference())).thenReturn("reference"); assertSame("reference", documentConverter.convert(String.class, document)); }