What testing tools or libraries have you used in your work?

In working with Go, I often use the standard testing package for writing unit tests. It is simple and integrated into the language, which is convenient for basic testing.

For more complex cases, I use libraries:

• testify — provides convenient assertion functions and mock objects.
• gomock — for creating mocks of interfaces.
• httptest — for testing HTTP servers and clients.

An example of a simple test using testing:

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

I also sometimes use benchmarks from the testing package to evaluate performance.