TEST_CASE("HELP-101966: builder appends empty string value", "[bsoncxx::builder::basic]") {
    using namespace builder::basic;

    // An empty string element copied out of a document and re-appended must
    // remain a string, not become null.
    builder::basic::document source;
    builder::basic::document copy;
    builder::basic::document expected;

    source.append(kvp("foo", ""));
    expected.append(kvp("foo", ""));

    auto const elem = source.view()["foo"];

    copy.append(kvp(std::string{elem.key()}, elem.get_value()));

    viewable_eq_viewable(expected, copy); // Fails!
    //   expected = { "foo" : "" }
    //   basic = { "foo" : null }
}