Unit Testing and Integration Guide

Unit and integration testing for a cross-platform C++20 socket library can be quite challenging, but with the right approach and tools, it can be done effectively. Here's a structured plan to guide you through setting up unit and integration tests for your library.

1. Unit Tests:

Unit tests for a socket library typically test individual components of the library in isolation. You will mock or simulate socket-related functionality in your unit tests to avoid real network activity.

Tools for Unit Testing in C++20:

• Google Test (gtest): This is one of the most popular C++ testing frameworks, providing powerful features such as assertions, fixtures, and mock support. It works seamlessly on both Windows and Linux and integrates easily into CMake.
• Google Mock (gmock): This is an extension of Google Test that allows you to mock classes and methods. Useful for mocking socket behavior and testing edge cases where actual socket communication isn't needed.

1.1 Mocking Socket Behavior:

To unit test your socket library, you’ll need to mock socket-related functions like socket(), recv(), send(), etc. This allows you to test your socket code without actually opening real network connections.

Example: Using Google Mock to Mock recv and send:

1. Define a mock class for socket functions:

#include <gmock/gmock.h>
#include <sys/socket.h>
 
class MockSocket {
public:
    MOCK_METHOD(int, recv, (int sockfd, void *buf, size_t len, int flags), ());
    MOCK_METHOD(int, send, (int sockfd, const void *buf, size_t len, int flags), ());
};

1. Use Google Test and Mock in your test cases:

#include <gtest/gtest.h>
#include "MockSocket.h"
 
class MySocketTest : public ::testing::Test {
protected:
    MockSocket mockSocket;
};
 
TEST_F(MySocketTest, TestSocketRead) {
    // Mock the recv function to return a fixed value
    EXPECT_CALL(mockSocket, recv(::testing::_, ::testing::_, ::testing::_, ::testing::_))
        .WillOnce(::testing::Return(5));  // Simulate 5 bytes received
 
    // Call the function in your library that uses recv
    int result = mySocketLibraryReadFunction(mockSocket);
 
    ASSERT_EQ(result, 5);  // Assert that the result is as expected
}

1.2 Testing Socket Initialization and Cleanup:

You can test the initialization, error handling, and cleanup of sockets using mock or actual socket functions, but avoid creating real connections.

2. Integration Tests:

Integration tests test how components of the socket library interact with real resources (e.g., actual sockets, local servers, etc.). These tests typically involve starting up a real server and connecting with a client, or testing how the library handles real network connections in a controlled environment.

2.1 Setting Up Real Server and Client:

For integration testing, you'll want to set up a TCP server and TCP client that test the real communication.

1. Server Setup: Use your socket library to implement a simple server that listens for incoming connections.
2. Client Setup: Implement a client that connects to the server and sends/receives data.
3. Test Communication: The integration tests will simulate actual network communication and ensure your library correctly handles socket connections, sends and receives data, and closes connections.

Example of a Simple Server-Client Integration Test:

#include <gtest/gtest.h>
#include <thread>
#include "Socket.h"  // Your socket library
 
// Simple server that listens on a specific port
void startServer() {
    ServerSocket server(8080);
    server.listen();
    Socket client = server.accept();  // Accept a connection from the client
    char buffer[1024];
    client.read(buffer, sizeof(buffer));  // Read the data sent from the client
    client.write("ack", 3);  // Send an acknowledgment
    client.close();
}
 
// Simple client that connects to the server
void startClient() {
    Socket client("127.0.0.1", 8080);
    client.write("hello", 5);  // Send a message to the server
    char buffer[1024];
    client.read(buffer, sizeof(buffer));  // Read the server's acknowledgment
    client.close();
}
 
TEST(SocketIntegrationTest, TestServerClientCommunication) {
    // Run server in a separate thread
    std::thread serverThread(startServer);
 
    // Run client in the main thread
    startClient();
 
    serverThread.join();  // Ensure the server thread completes
 
    // Add assertions here, if necessary, to verify the data exchange
}

3. Test Coverage for Cross-Platform:

Since your library is cross-platform, it's important to ensure that tests work on both Windows and Linux (or other platforms). Here are a few strategies to ensure cross-platform testing:

• CMake Presets: Use CMake presets to configure the build system for different platforms.
• Docker: For testing on Linux, you can use Docker containers to simulate different Linux environments.
• CI/CD Pipelines: Set up continuous integration (CI) pipelines to automatically run your tests on both Windows and Linux environments.

For example, use GitHub Actions, Travis CI, or AppVeyor to run your tests on multiple platforms.

3.1 Using CMake for Platform-Specific Tests:

You can specify platform-specific configurations in your CMakeLists.txt to manage platform-specific test setups.

if (WIN32)
    add_executable(SocketTestWindows test_socket.cpp)
    target_link_libraries(SocketTestWindows gtest gmock)
    set_target_properties(SocketTestWindows PROPERTIES
            COMPILE_DEFINITIONS "PLATFORM_WINDOWS"
    )
elseif (UNIX)
    add_executable(SocketTestUnix test_socket.cpp)
    target_link_libraries(SocketTestUnix gtest gmock)
    set_target_properties(SocketTestUnix PROPERTIES
            COMPILE_DEFINITIONS "PLATFORM_LINUX"
    )
endif ()

4. Mocking or Stubbing Socket API for Unit Tests:

For unit tests where you don't want to deal with actual network communication, you can mock socket calls like socket(), recv(), send(), and close() to simulate different network conditions.

Mock Example with Google Mock:

class MockSocketAPI {
public:
    MOCK_METHOD(int, socket, (int domain, int type, int protocol), ());
    MOCK_METHOD(int, send, (int sockfd, const void *buf, size_t len, int flags), ());
    MOCK_METHOD(int, recv, (int sockfd, void *buf, size_t len, int flags), ());
    MOCK_METHOD(int, close, (int sockfd), ());
};

4.1 Integration Test with Mocking:

You can mock system calls for a more controlled environment during unit tests. This way, you can simulate various network conditions without needing a live server or network connection.

5. Test Cases to Consider:

Here are some potential test cases for your socket library:

• Connection Tests:
  • Can you successfully connect a client to a server?
  • What happens when the server is unavailable?
  • Can the server handle multiple simultaneous clients?
• Timeouts:
  • Does the socket properly handle timeouts for both reading and writing?
• Data Handling:
  • Can the socket send and receive data reliably?
  • Does the socket handle large data transfers?
• Error Handling:
  • What happens when an invalid socket is used?
  • Does the library throw exceptions for failed operations?

Conclusion:

• Unit Tests: Mock socket functions to test socket operations in isolation without actual network communication.
• Integration Tests: Set up real server-client communication to test the full flow of data over TCP connections.
• Cross-Platform Support: Ensure your tests work on both Windows and Linux by using CI/CD tools and platform-specific build configurations.

By leveraging Google Test, Google Mock, and CI pipelines, you can ensure your cross-platform socket library is robust and works as expected across different systems.

Let me know if you need further help or more examples!