Add new tests cases & test housekeeping

Summary:
related to T12015
- error.hpp covered
- assemble_op.hpp fully covered
- malformed_pubrel test is now functional
- attempt at using fixtures in malformed_packet.cpp test suite to
lower the amount of copy-paste code lines
- test coverage ~89%

Reviewers: ivica

Reviewed By: ivica

Subscribers: miljen, iljazovic

Differential Revision: https://repo.mireo.local/D27395

test/unit/error.cpp

@@ -0,0 +1,83 @@
+#include <boost/test/unit_test.hpp>
+
+#include <sstream>
+#include <vector>
+
+#include <async_mqtt5/error.hpp>
+
+using namespace async_mqtt5;
+
+BOOST_AUTO_TEST_SUITE(error/*, *boost::unit_test::disabled()*/)
+
+BOOST_AUTO_TEST_CASE(client_ec_to_string) {
+	// Ensure that all branches of the switch/case are covered
+
+	std::vector<client::error> ecs = {
+		client::error::malformed_packet,
+		client::error::packet_too_large,
+		client::error::session_expired,
+		client::error::pid_overrun,
+		client::error::invalid_topic,
+		client::error::qos_not_supported,
+		client::error::retain_not_available,
+		client::error::topic_alias_maximum_reached,
+		client::error::wildcard_subscription_not_available,
+		client::error::subscription_identifier_not_available,
+		client::error::shared_subscription_not_available
+	};
+
+	const client::client_ec_category& cat = client::get_error_code_category();
+	BOOST_CHECK_NO_THROW(cat.name());
+
+	constexpr auto default_output = "Unknown client error.";
+	for (auto ec : ecs)
+		BOOST_CHECK(cat.message(static_cast<int>(ec)) != default_output);
+
+	// default branch
+	BOOST_CHECK(cat.message(1) == default_output);
+}
+
+
+BOOST_AUTO_TEST_CASE(reason_code_to_string) {
+	// Ensure that all branches of the switch/case are covered
+	using namespace reason_codes;
+
+	std::vector<reason_code> rcs = {
+		empty, success, normal_disconnection,
+		granted_qos_0, granted_qos_1, granted_qos_2,
+		disconnect_with_will_message, no_matching_subscribers,
+		no_subscription_existed, continue_authentication, reauthenticate,
+		unspecified_error, malformed_packet, protocol_error,
+		implementation_specific_error, unsupported_protocol_version,
+		client_id_not_valid,bad_username_or_password,
+		not_authorized, server_unavailable, server_busy, banned,
+		server_shutting_down, bad_authentication_method, keep_alive_timeout,
+		session_taken_over, topic_filter_invalid,topic_name_invalid,
+		packet_id_in_use, packet_id_not_found, receive_maximum_exceeded,
+		topic_alias_invalid, packet_too_large, message_rate_too_high,
+		quota_exceeded, administrative_action, payload_format_invalid,
+		retain_not_supported, qos_not_supported, use_another_server,
+		server_moved, shared_subscriptions_not_supported, connection_rate_exceeded,
+		maximum_connect_time, subscription_ids_not_supported,
+		wildcard_subscriptions_not_supported
+	};
+
+	BOOST_CHECK_EQUAL(rcs.size(), 46);
+
+	constexpr auto default_output = "Invalid reason code";
+	for (const auto& rc: rcs) 
+		BOOST_CHECK(rc.message() != "Invalid reason code");
+
+	// default branch
+	BOOST_CHECK(
+		reason_code(0x05, reason_codes::category::suback).message() == default_output
+	);
+}
+
+BOOST_AUTO_TEST_CASE(reason_code_to_stream) {
+	std::ostringstream stream;
+	stream << reason_codes::success;
+	BOOST_CHECK_EQUAL(stream.str(), reason_codes::success.message());
+}
+
+BOOST_AUTO_TEST_SUITE_END();