func TestGenerateCharactersSmallExclude(t *testing.T) {
    exclude := []byte{1, 2, 3, 4, 5}
    data := generateCharacters(exclude)
    if len(data) != 256 - len(exclude) {
        t.Errorf("len(characters(exclude) = %d, want %d", len(data),
            256 - len(exclude))
    }
}
tests characters generation with some exclusions
package overflow
import (
    "testing"
)
func TestGenerateCharactersNoExclude(t *testing.T) {
    data := generateCharacters([]byte{})
    if len(data) != 256 {
        t. Errorf("len(characters([]byte{}) = %d, want %d", len(data), 256)
    }
}