What tests do you consider the most effective?

The most effective types of tests I consider are:

• Unit tests — check individual functions or methods, run quickly, and help identify errors early.
• Integration tests — verify interaction between components, identify issues at module interfaces.
• E2E (end-to-end) tests — simulate application operation from the user's perspective, test the entire flow from start to finish.

In Go, unit tests with the testing package are often used because they are fast and simple. To improve efficiency, it is important to write tests that cover critical business logic and possible boundary cases, and also keep tests up to date.

An example of a simple unit test in Go:

func Add(a, b int) int {
    return a + b
}

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