How to write unit tests for logging functionality in Go code?

Writing unit tests for logging functionality in Go code can be done by following these steps:

Import the necessary testing and logging packages:

import (
	"testing"
	"log"
)

Create a mock logger that implements the logging interface you're using in your code:

type mockLogger struct {
	logs []string
}

func (m *mockLogger) Log(s string) {
	m.logs = append(m.logs, s)
}

In your test function, replace the actual logger with the mock logger:

func TestSomeLoggingFunction(t *testing.T) {
	originalLogger := logger // Store the original logger
	logger = &mockLogger{}   // Use the mock logger for testing
	defer func() { logger = originalLogger }()

	// Run the function that uses logging
	someLoggingFunction()

	// Verify the logs
	expectedLogs := []string{"log1", "log2", "log3"} // Define the expected logs
	mock := logger.(*mockLogger)                    // Type cast the logger to the mock logger
	if !reflect.DeepEqual(expectedLogs, mock.logs) { // Compare expected logs with the actual logs
		t.Errorf("Expected logs %v, but got %v", expectedLogs, mock.logs)
	}
}

The test function can now verify the logs recorded by the mock logger and raise an error if they do not match the expected logs.

Note: This example assumes that the logging API you're using has a Log method, which is implemented by the logging interface. Modify the mock logger's Log method accordingly.

By executing these steps, you can effectively write unit tests for logging functionality in your Go code.