What is the purpose of using unit tests in software development?

Unit tests are designed to verify the correctness of individual components (modules) of a program in isolation from the rest of the system. Their main goals:

• Detect errors in the code early.
• Simplify debugging, as tests are localized to specific functions or classes.
• Improve the quality and reliability of the code.
• Facilitate refactoring by ensuring that changes do not break existing functionality.
• Serve as documentation for module usage.

For example, in Go, a unit test is usually written in a file with the suffix _test.go and uses the testing package:

func TestSum(t *testing.T) {
    result := Sum(2, 3)
    if result != 5 {
        t.Errorf("Expected 5, got %d", result)
    }
}