message: Change stream tests require replica set
diff: #include <mongocxx/instance.hpp>
  #include <mongocxx/pipeline.hpp>
  #include <mongocxx/private/libbson.hh>
  +#include <mongocxx/test_util/client_helpers.hh>
  #include <third_party/catch/include/helpers.hpp>
  @@ -196,6 +197,11 @@ TEST_CASE("Mock streams and error-handling") {
  TEST_CASE("Watch a non-existent collection", "[min36]") {
  instance::current();
  client mongodb_client{uri{}};
  + if (!test_util::is_replica_set(mongodb_client)) {
  + WARN("skip: change streams require replica set");
  + return;
  + }
  +
  options::change_stream options{};
  database db = mongodb_client["does_not_exist"];
  @@ -209,6 +215,11 @@ TEST_CASE("Watch a non-existent collection", "[min36]") {
  TEST_CASE("Create streams.events and assert we can read a single event", "[min36]") {
  instance::current();
  client mongodb_client{uri{}};
  + if (!test_util::is_replica_set(mongodb_client)) {
  + WARN("skip: change streams require replica set");
  + return;
  + }
  +
  collection events = mongodb_client["streams"]["events"];
  events.drop();
  @@ -225,6 +236,11 @@ TEST_CASE("Create streams.events and assert we can read a single event", "[min36
  TEST_CASE("Give an invalid pipeline", "[min36]") {
  instance::current();
  client mongodb_client{uri{}};
  + if (!test_util::is_replica_set(mongodb_client)) {
  + WARN("skip: change streams require replica set");
  + return;
  + }
  +
  options::change_stream options{};
  collection events = mongodb_client["streams"]["events"];
  @@ -250,6 +266,11 @@ TEST_CASE("Give an invalid pipeline", "[min36]") {
  TEST_CASE("Documentation Examples", "[min36]") {
  instance::current();
  client mongodb_client{uri{}};
  + if (!test_util::is_replica_set(mongodb_client)) {
  + WARN("skip: change streams require replica set");
  + return;
  + }
  +
  options::change_stream options{};
  collection events = mongodb_client["streams"]["events"];
  @@ -292,6 +313,11 @@ TEST_CASE("Documentation Examples", "[min36]") {
  TEST_CASE("Watch 2 collections", "[min36]") {
  instance::current();
  client mongodb_client{uri{}};
  + if (!test_util::is_replica_set(mongodb_client)) {
  + WARN("skip: change streams require replica set");
  + return;
  + }
  +
  options::change_stream options{};
  collection events = mongodb_client["streams"]["events"];
  @@ -335,6 +361,11 @@ TEST_CASE("Watch 2 collections", "[min36]") {
  TEST_CASE("Watch a Collection", "[min36]") {
  instance::current();
  client mongodb_client{uri{}};
  + if (!test_util::is_replica_set(mongodb_client)) {
  + WARN("skip: change streams require replica set");
  + return;
  + }
  +
  options::change_stream options{};
  collection events = mongodb_client["streams"]["events"];
  