text: package pflag
  
  import (
  	"fmt"
  	"net"
  	"os"
  	"testing"
  )
  
  func setUpIP(ip *net.IP) *FlagSet {
  	f := NewFlagSet("test", ContinueOnError)
  	f.IPVar(ip, "address", net.ParseIP("0.0.0.0"), "IP Address")
  	return f
  }
  
  func TestIP(t *testing.T) {
  	testCases := []struct {
  		input    string
  		success  bool
  		expected string
  	}{
  		{"0.0.0.0", true, "0.0.0.0"},
  		{" 0.0.0.0 ", true, "0.0.0.0"},
  		{"1.2.3.4", true, "1.2.3.4"},
  		{"127.0.0.1", true, "127.0.0.1"},
  		{"255.255.255.255", true, "255.255.255.255"},
  		{"", false, ""},
  		{"0", false, ""},
  		{"localhost", false, ""},
  		{"0.0.0", false, ""},
  		{"0.0.0.", false, ""},
  		{"0.0.0.0.", false, ""},
  		{"0.0.0.256", false, ""},
  		{"0 . 0 . 0 . 0", false, ""},
  	}
  
  	devnull, _ := os.Open(os.DevNull)
  	os.Stderr = devnull
  	for i := range testCases {
  		var addr net.IP
  		f := setUpIP(&addr)
  
  		tc := &testCases[i]
  
  		arg := fmt.Sprintf("--address=%s", tc.input)
  		err := f.Parse([]string{arg})
  		if err != nil && tc.success == true {
  			t.Errorf("expected success, got %q", err)
  			continue
  		} else if err == nil && tc.success == false {
  			t.Errorf("expected failure")
  			continue
  		} else if tc.success {
  			ip, err := f.GetIP("address")
  			if err != nil {
  				t.Errorf("Got error trying to fetch the IP flag: %v", err)
  			}
  			if ip.String() != tc.expected {
  				t.Errorf("expected %q, got %q", tc.expected, ip.String())
  			}
  		}
  	}
  }
  